The Equalizer S03E10 - The Rehearsal

McCall and Gage attend the rehearsal of a play in which the daughter of an associate will be starring. While she's in her dressing room, a shadowy figure tells her to leave. Later they discover that someone has cut the phone lines and booby trapped the theatre so when anyone comes inside, the bomb will go off. So they have to find the one who planted it so they can deactivate it. And it's while they wait that they discover that the people there know more than they are telling.