The fifth season finale of "Castle" (10 p.m., 6 ABC) finds Castle (Nathan Fillion) and Beckett (Stana Katic) facing yet another romantic obstacle, as Beckett's offered a job with the feds that would take her to Washington, D.C. (why this is a problem for Castle, whose job as a bestelling novelist can be done just about anywhere, is hard to say). Also, there's a murder investigation. But you knew that already.
On a more serious note, "Independent Lens' (10 p.m., WHYY 12) airs the 90-minute film "Invisible War," which looks at rape in the U.S. military and why it so often goes unpunished.
CBS is hyping the Season 8 finale of "How I Met Your Mother" (8 p.m., CBS 3), but just the fact that it's the Season 8 finale and not the series finale is enough to make me suspicious that even if we finally learn about the woman who's going to transform Josh Radnor into Bob Saget it'll happen in such a way that we'll feel cheated, anyway. Or maybe that's already happened? Because I'm afraid I stopped watching regularly several seasons ago.