'Pretty Little Liars'
Caleb returns to the show after that whole spin-off series didn't work out so well. Welcome back, Caleb. Looks like he got a haircut, which is undoubtedly the work of the nefarious "A."
8 p.m., ABCFAM
Evan tries to talk to a woman with a mysterious illness in the hopes of bringing her to Hank, who could use his super powered doctor brain to figure out what's going on with her.
9 p.m., USA
'The Wil Wheaton Project'
The motion capture master Andy Serkis stops by the show. You may have seen, well, not him, but his motion capture antics as Gollum and King Kong.
9 p.m., SYFY
'The Late Show with David Letterman'
Joan Rivers stops by, which would be less newsworthy if not for the fact that she stormed out of another interview over the weekend. Will she walk out on Dave? Probably not.
11:35 p.m., CBS