diff --git a/src/main.rs b/src/main.rs
index e1d4453..7231af8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -32,6 +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.as_str()).map_err(|e| e.to_string())?;
+    let owner_tree = build_owner_tree(body.as_str(), ast.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 aadf7e6..d45fe90 100644
--- a/src/owner_tree.rs
+++ b/src/owner_tree.rs
@@ -1,12 +1,122 @@
 use serde::Serialize;
 
-use crate::sexp::sexp_with_padding;
+use crate::sexp::{sexp_with_padding, Token};
 
-pub fn build_owner_tree(file_contents: &str) -> Result<OwnerTree, Box<dyn std::error::Error + '_>> {
-    let (_remaining, parsed_sexp) = sexp_with_padding(file_contents)?;
+pub fn build_owner_tree<'a>(
+    body: &'a str,
+    ast_raw: &'a str,
+) -> Result<OwnerTree, Box<dyn std::error::Error + 'a>> {
+    let (_remaining, parsed_sexp) = sexp_with_padding(ast_raw)?;
+    let lists = find_lists_in_document(&parsed_sexp)?;
 
-    Ok(OwnerTree {})
+    Ok(OwnerTree {
+        ast: ast_raw.to_owned(),
+        children: lists,
+    })
 }
 
 #[derive(Serialize)]
-pub struct OwnerTree {}
+pub struct OwnerTree {
+    ast: String,
+    children: Vec<PlainList>,
+}
+
+#[derive(Serialize)]
+pub struct PlainList {
+    position: SourceRange,
+    children: Vec<PlainListItem>,
+}
+
+#[derive(Serialize)]
+pub struct PlainListItem {
+    position: SourceRange,
+    children: Vec<PlainListItem>,
+}
+
+#[derive(Serialize)]
+pub struct SourceRange {
+    start_line: u32,
+    end_line: u32, // Exclusive
+    start_character: u32,
+    end_character: u32, // Exclusive
+}
+
+fn find_lists_in_document<'a>(
+    current_token: &Token<'a>,
+) -> Result<Vec<PlainList>, Box<dyn std::error::Error>> {
+    // DFS looking for top-level lists
+
+    let mut found_lists = Vec::new();
+    let children = current_token.as_list()?;
+    let token_name = "org-data";
+    assert_name(current_token, token_name)?;
+
+    // skip 2 to skip token name and standard properties
+    for child_token in children.iter().skip(2) {
+        found_lists.extend(recurse_token(child_token)?);
+    }
+
+    Ok(found_lists)
+}
+
+fn assert_name<'s>(emacs: &'s Token<'s>, name: &str) -> Result<(), Box<dyn std::error::Error>> {
+    let children = emacs.as_list()?;
+    let first_child = children
+        .first()
+        .ok_or("Should have at least one child.")?
+        .as_atom()?;
+    if first_child != name {
+        Err(format!(
+            "Expected a {expected} cell, but found a {found} cell.",
+            expected = name,
+            found = first_child
+        ))?;
+    }
+    Ok(())
+}
+
+fn recurse_token<'a>(
+    current_token: &Token<'a>,
+) -> Result<Vec<PlainList>, Box<dyn std::error::Error>> {
+    match current_token {
+        Token::Atom(_) | Token::TextWithProperties(_) => Ok(Vec::new()),
+        Token::List(_) => {
+            let new_lists = find_lists_in_list(current_token)?;
+            Ok(new_lists)
+        }
+        Token::Vector(_) => {
+            let new_lists = find_lists_in_vector(current_token)?;
+            Ok(new_lists)
+        }
+    }
+}
+
+fn find_lists_in_list<'a>(
+    current_token: &Token<'a>,
+) -> Result<Vec<PlainList>, Box<dyn std::error::Error>> {
+    let mut found_lists = Vec::new();
+    let children = current_token.as_list()?;
+    if assert_name(current_token, "plain-list").is_ok() {
+        // Found a list!
+    }
+
+    // skip 2 to skip token name and standard properties
+    for child_token in children.iter().skip(2) {
+        found_lists.extend(recurse_token(child_token)?);
+    }
+
+    Ok(found_lists)
+}
+
+fn find_lists_in_vector<'a>(
+    current_token: &Token<'a>,
+) -> Result<Vec<PlainList>, Box<dyn std::error::Error>> {
+    let mut found_lists = Vec::new();
+    let children = current_token.as_vector()?;
+
+    for child_token in children.iter() {
+        found_lists.extend(recurse_token(child_token)?);
+    }
+
+    Ok(found_lists)
+}