chmspec-0.1.3-html/Internal.html#TOCIDX

>   5.3.7. #TOCIDX
>   Table 5.10. 20/28 byte structures
>
>   4   DWORD   Seems to be a bit field:
>               0x2 is whether or not New is turned on,
>               0x4 is set when the entry is a book/has children and
>               0x8 is set when the entry has a Local value.
>
>   8   DWORD   Unknown. In some cases it is an index into the #TOPICS file
>               of the entry containing offsets to the title & filename.

Check the bitflags at offset 0x04. If this node has children (bit 0x4 is set) but has no Local value (bit 0x8 is clear), then the DWORD at offset 0x08 is an offset into the #STRINGS file. Otherwise, the DWORD at offset 0x08 is an index into the #TOPICS file.