TocJS Transformation Does not Generate All Files for a Tree-Like TOC

Problem

The TocJS transformation of a DITA map does not generate all the files needed to display the tree-like table of contents.

To get a complete set of output files, follow these steps:

Run the XHTML transformation on the same DITA map. Make sure the output gets generated in the same output folder as for the TocJS transformation.
Copy the content of the DITA-OT-DIR/plugins/com.sophos.tocjs/basefiles folder to the transformation output folder.
Copy the DITA-OT-DIR/plugins/com.sophos.tocjs/sample/basefiles/frameset.html file to the transformation output folder.
Edit frameset.html file.
Locate element <frame name="contentwin" src="concepts/about.html">.
Replace "concepts/about.html" with "index.html".