diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..37e3804
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,25 @@
+use nom::error::ErrorKind;
+use nom::error::ParseError;
+use nom::IResult;
+
+pub type Res<T, U> = IResult<T, U, CustomError<T>>;
+
+#[derive(Debug, PartialEq)]
+pub enum CustomError<I> {
+    MyError(MyError<I>),
+    Nom(I, ErrorKind),
+}
+
+#[derive(Debug, PartialEq)]
+pub struct MyError<I>(pub I);
+
+impl<I> ParseError<I> for CustomError<I> {
+    fn from_error_kind(input: I, kind: ErrorKind) -> Self {
+        CustomError::Nom(input, kind)
+    }
+
+    fn append(_input: I, _kind: ErrorKind, /*mut*/ other: Self) -> Self {
+        // Doesn't do append like VerboseError
+        other
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 982be1b..e1d4453 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,8 +4,10 @@ use owner_tree::{build_owner_tree, OwnerTree};
 use parse::emacs_parse_org_document;
 use tower_http::services::{ServeDir, ServeFile};
 
+mod error;
 mod owner_tree;
 mod parse;
+mod sexp;
 
 #[tokio::main]
 async fn main() {
@@ -30,6 +32,6 @@ async fn _parse_org_mode(
     body: String,
 ) -> Result<(StatusCode, Json<OwnerTree>), Box<dyn std::error::Error>> {
     let ast = emacs_parse_org_document(&body).await?;
-    let owner_tree = build_owner_tree(body)?;
+    let owner_tree = build_owner_tree(body.as_str()).map_err(|e| e.to_string())?;
     Ok((StatusCode::OK, Json(owner_tree)))
 }
diff --git a/src/owner_tree.rs b/src/owner_tree.rs
index ee2aaf5..aadf7e6 100644
--- a/src/owner_tree.rs
+++ b/src/owner_tree.rs
@@ -1,15 +1,12 @@
 use serde::Serialize;
 
-pub fn build_owner_tree<C>(file_contents: C) -> Result<OwnerTree, Box<dyn std::error::Error>>
-where
-    C: AsRef<str>,
-{
-    Ok(OwnerTree {
-        input_source: file_contents.as_ref().to_owned(),
-    })
+use crate::sexp::sexp_with_padding;
+
+pub fn build_owner_tree(file_contents: &str) -> Result<OwnerTree, Box<dyn std::error::Error + '_>> {
+    let (_remaining, parsed_sexp) = sexp_with_padding(file_contents)?;
+
+    Ok(OwnerTree {})
 }
 
 #[derive(Serialize)]
-pub struct OwnerTree {
-    input_source: String,
-}
+pub struct OwnerTree {}
diff --git a/src/sexp.rs b/src/sexp.rs
new file mode 100644
index 0000000..1a7aa4c
--- /dev/null
+++ b/src/sexp.rs
@@ -0,0 +1,368 @@
+use std::collections::HashMap;
+
+use nom::branch::alt;
+use nom::bytes::complete::escaped;
+use nom::bytes::complete::tag;
+use nom::bytes::complete::take_till1;
+use nom::character::complete::multispace0;
+use nom::character::complete::multispace1;
+use nom::character::complete::one_of;
+use nom::combinator::map;
+use nom::combinator::not;
+use nom::combinator::opt;
+use nom::combinator::peek;
+use nom::multi::separated_list1;
+use nom::sequence::delimited;
+use nom::sequence::preceded;
+use nom::sequence::tuple;
+
+use crate::error::Res;
+
+#[derive(Debug)]
+pub enum Token<'s> {
+    Atom(&'s str),
+    List(Vec<Token<'s>>),
+    TextWithProperties(TextWithProperties<'s>),
+    Vector(Vec<Token<'s>>),
+}
+
+#[derive(Debug)]
+pub struct TextWithProperties<'s> {
+    #[allow(dead_code)]
+    pub text: &'s str,
+    #[allow(dead_code)]
+    pub properties: Vec<Token<'s>>,
+}
+
+impl<'s> TextWithProperties<'s> {
+    pub fn unquote(&self) -> Result<String, Box<dyn std::error::Error>> {
+        let mut out = String::with_capacity(self.text.len());
+        if !self.text.starts_with(r#"""#) {
+            return Err("Quoted text does not start with quote.".into());
+        }
+        if !self.text.ends_with(r#"""#) {
+            return Err("Quoted text does not end with quote.".into());
+        }
+        let interior_text = &self.text[1..(self.text.len() - 1)];
+        let mut state = ParseState::Normal;
+        for current_char in interior_text.chars().into_iter() {
+            state = match (state, current_char) {
+                (ParseState::Normal, '\\') => ParseState::Escape,
+                (ParseState::Normal, _) => {
+                    out.push(current_char);
+                    ParseState::Normal
+                }
+                (ParseState::Escape, 'n') => {
+                    out.push('\n');
+                    ParseState::Normal
+                }
+                (ParseState::Escape, '\\') => {
+                    out.push('\\');
+                    ParseState::Normal
+                }
+                (ParseState::Escape, '"') => {
+                    out.push('"');
+                    ParseState::Normal
+                }
+                _ => todo!(),
+            };
+        }
+
+        Ok(out)
+    }
+}
+
+enum ParseState {
+    Normal,
+    Escape,
+}
+
+impl<'s> Token<'s> {
+    pub fn as_vector<'p>(&'p self) -> Result<&'p Vec<Token<'s>>, Box<dyn std::error::Error>> {
+        Ok(match self {
+            Token::Vector(children) => Ok(children),
+            _ => Err(format!("wrong token type {:?}", self)),
+        }?)
+    }
+
+    pub fn as_list<'p>(&'p self) -> Result<&'p Vec<Token<'s>>, Box<dyn std::error::Error>> {
+        Ok(match self {
+            Token::List(children) => Ok(children),
+            _ => Err(format!("wrong token type {:?}", self)),
+        }?)
+    }
+
+    pub fn as_atom<'p>(&'p self) -> Result<&'s str, Box<dyn std::error::Error>> {
+        Ok(match self {
+            Token::Atom(body) => Ok(*body),
+            _ => Err(format!("wrong token type {:?}", self)),
+        }?)
+    }
+
+    pub fn as_text<'p>(&'p self) -> Result<&'p TextWithProperties<'s>, Box<dyn std::error::Error>> {
+        Ok(match self {
+            Token::TextWithProperties(body) => Ok(body),
+            _ => Err(format!("wrong token type {:?}", self)),
+        }?)
+    }
+
+    pub fn as_map<'p>(
+        &'p self,
+    ) -> Result<HashMap<&'s str, &'p Token<'s>>, Box<dyn std::error::Error>> {
+        let mut hashmap = HashMap::new();
+
+        let children = self.as_list()?;
+        if children.len() % 2 != 0 {
+            return Err("Expecting an even number of children".into());
+        }
+        let mut key: Option<&str> = None;
+        for child in children.iter() {
+            match key {
+                None => {
+                    key = Some(child.as_atom()?);
+                }
+                Some(key_val) => {
+                    key = None;
+                    hashmap.insert(key_val, child);
+                }
+            };
+        }
+
+        Ok(hashmap)
+    }
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+pub fn sexp_with_padding<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, _) = multispace0(input)?;
+    let (remaining, tkn) = token(remaining)?;
+    let (remaining, _) = multispace0(remaining)?;
+    Ok((remaining, tkn))
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+pub fn sexp<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, tkn) = token(input)?;
+    Ok((remaining, tkn))
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn token<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    alt((list, vector, atom))(input)
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn list<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, _) = tag("(")(input)?;
+    let (remaining, children) = delimited(
+        multispace0,
+        separated_list1(multispace1, token),
+        multispace0,
+    )(remaining)?;
+    let (remaining, _) = tag(")")(remaining)?;
+    Ok((remaining, Token::List(children)))
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn vector<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, _) = tag("[")(input)?;
+    let (remaining, children) = delimited(
+        multispace0,
+        separated_list1(multispace1, token),
+        multispace0,
+    )(remaining)?;
+    let (remaining, _) = tag("]")(remaining)?;
+    Ok((remaining, Token::Vector(children)))
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn atom<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    not(peek(one_of(")]")))(input)?;
+    alt((
+        text_with_properties,
+        hash_notation,
+        quoted_atom,
+        unquoted_atom,
+    ))(input)
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn unquoted_atom<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, body) = take_till1(|c| match c {
+        ' ' | '\t' | '\r' | '\n' | ')' | ']' => true,
+        _ => false,
+    })(input)?;
+    Ok((remaining, Token::Atom(body)))
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn quoted_atom<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, _) = tag(r#"""#)(input)?;
+    let (remaining, _) = escaped(
+        take_till1(|c| match c {
+            '\\' | '"' => true,
+            _ => false,
+        }),
+        '\\',
+        one_of(r#""n\\"#),
+    )(remaining)?;
+    let (remaining, _) = tag(r#"""#)(remaining)?;
+    let source = get_consumed(input, remaining);
+    Ok((remaining, Token::Atom(source)))
+}
+
+#[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
+fn hash_notation<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, _) = tag("#<")(input)?;
+    let (remaining, _body) = take_till1(|c| match c {
+        '>' => true,
+        _ => false,
+    })(remaining)?;
+    let (remaining, _) = tag(">")(remaining)?;
+    let source = get_consumed(input, remaining);
+    Ok((remaining, Token::Atom(source)))
+}
+
+fn text_with_properties<'s>(input: &'s str) -> Res<&'s str, Token<'s>> {
+    let (remaining, _) = tag("#(")(input)?;
+    let (remaining, (text, props)) = delimited(
+        multispace0,
+        tuple((
+            map(quoted_atom, |atom| match atom {
+                Token::Atom(body) => body,
+                _ => unreachable!(),
+            }),
+            preceded(multispace1, opt(separated_list1(multispace1, token))),
+        )),
+        multispace0,
+    )(remaining)?;
+    let (remaining, _) = tag(")")(remaining)?;
+    Ok((
+        remaining,
+        Token::TextWithProperties(TextWithProperties {
+            text,
+            properties: props.unwrap_or(Vec::new()),
+        }),
+    ))
+}
+
+/// Get a slice of the string that was consumed in a parser using the original input to the parser and the remaining input after the parser.
+fn get_consumed<'s>(input: &'s str, remaining: &'s str) -> &'s str {
+    assert!(is_slice_of(input, remaining));
+    let source = {
+        let offset = remaining.as_ptr() as usize - input.as_ptr() as usize;
+        &input[..offset]
+    };
+    source
+}
+
+/// Check if the child string slice is a slice of the parent string slice.
+fn is_slice_of(parent: &str, child: &str) -> bool {
+    let parent_start = parent.as_ptr() as usize;
+    let parent_end = parent_start + parent.len();
+    let child_start = child.as_ptr() as usize;
+    let child_end = child_start + child.len();
+    child_start >= parent_start && child_end <= parent_end
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn simple() {
+        let input = "  (foo bar baz )  ";
+        let (remaining, parsed) = sexp_with_padding(input).expect("Parse the input");
+        assert_eq!(remaining, "");
+        assert!(match parsed {
+            Token::Atom(_) => false,
+            Token::List(_) => true,
+            Token::TextWithProperties(_) => false,
+            Token::Vector(_) => false,
+        });
+    }
+
+    #[test]
+    fn quoted() {
+        let input = r#"  ("foo" bar baz )  "#;
+        let (remaining, parsed) = sexp_with_padding(input).expect("Parse the input");
+        assert_eq!(remaining, "");
+        assert!(match parsed {
+            Token::Atom(_) => false,
+            Token::List(_) => true,
+            Token::TextWithProperties(_) => false,
+            Token::Vector(_) => false,
+        });
+        let children = match parsed {
+            Token::List(children) => children,
+            _ => panic!("Should be a list."),
+        };
+        assert_eq!(
+            match children.first() {
+                Some(Token::Atom(body)) => *body,
+                _ => panic!("First child should be an atom."),
+            },
+            r#""foo""#
+        )
+    }
+
+    #[test]
+    fn quoted_containing_paren() {
+        let input = r#"  (foo "b(a)r" baz )  "#;
+        let (remaining, parsed) = sexp_with_padding(input).expect("Parse the input");
+        assert_eq!(remaining, "");
+        assert!(match parsed {
+            Token::List(_) => true,
+            _ => false,
+        });
+        let children = match parsed {
+            Token::List(children) => children,
+            _ => panic!("Should be a list."),
+        };
+        assert_eq!(
+            match children.first() {
+                Some(Token::Atom(body)) => *body,
+                _ => panic!("First child should be an atom."),
+            },
+            r#"foo"#
+        );
+        assert_eq!(
+            match children.iter().nth(1) {
+                Some(Token::Atom(body)) => *body,
+                _ => panic!("Second child should be an atom."),
+            },
+            r#""b(a)r""#
+        );
+        assert_eq!(
+            match children.iter().nth(2) {
+                Some(Token::Atom(body)) => *body,
+                _ => panic!("Third child should be an atom."),
+            },
+            r#"baz"#
+        );
+    }
+
+    #[test]
+    fn string_containing_escaped_characters() {
+        let input = r#"  (foo "\\( x=2 \\)" bar)  "#;
+        let (remaining, parsed) = sexp_with_padding(input).expect("Parse the input");
+        assert_eq!(remaining, "");
+        assert!(match parsed {
+            Token::Atom(_) => false,
+            Token::List(_) => true,
+            Token::TextWithProperties(_) => false,
+            Token::Vector(_) => false,
+        });
+        let children = match parsed {
+            Token::List(children) => children,
+            _ => panic!("Should be a list."),
+        };
+        assert_eq!(
+            match children.get(1) {
+                Some(Token::Atom(body)) => *body,
+                _ => panic!("First child should be an atom."),
+            },
+            r#""\\( x=2 \\)""#
+        )
+    }
+}