Wednesday:

makes a welcome return in the Season 12 finale of “Criminal Minds.” Reprising his role as Derek Morgan, he brings the BAU a lead in the case against serial killer and escaped convict Mr. Scratch. 9 p.m., CBS.

Uh-oh. On the season finale of “Black-ish,” Dre decides to throw an unforgettable baby shower for Bow. But his plans are put on hold when she visits her ob-gyn with a headache and discovers she’s having complications. 9:30 p.m., ABC.

Season 2 of the historical drama “Underground” wraps up as Rosalee and Noah come face-to-face with Cato. Meanwhile, strategies change when Harriet Tubman is recruited by Jim Brown’s men. 10 p.m., WGN America.

Wednesday: Thursday:

It sounds like trouble could be brewing on the season finale of “The Big Bang Theory.” The gang is concerned when Sheldon’s former admirer, Dr. Ramona Nowitzki (Riki Lindhome), resurfaces while Amy is away at Princeton. 8 p.m., CBS.

McGarrett is risking his life yet again as “Hawaii Five-0” ends its season. The team attempts its “most dangerous rescue yet,” trying to save young girls trapped in the sex trafficking ring it has been tracking this year. 9 p.m., CBS.

Melissa McCarthy, who has earned raves on “Saturday Night Live” for her impersonation of White House Press Secretary Sean Spicer, returns to the show — this time as host. She’ll be joined by musical guest, HAIM. 11:30 p.m., NBC.

Friday: Saturday: