> I'm unable to make it work on "offline" captured
> site links. Is it possible to just grab a page from
> a reference link so that it too can be viewed
> offline?  

By default HTT only captures the starting site. So links in an offline site
would all be external. 
Either you need to add filters to allow specific external sites or use
external depth.
If you mirror the mirror with external depth = 10 you should get them. Or you
could just Update the mirror with external depth.
Currently External Depth is broken. So Htt will not stop at the intended limit
however.