24 Pearl, 10.35pm Dennis Hopper joins the series for the season's remaining five episodes as the mastermind behind the conspiracy. His identity and motives for seeking vengeance against David Palmer (Dennis Haysbert) and the Bauer family are revealed during this taut episode, in which Jack (Kiefer Sutherland) continues searching for clues as to why the Drazens had planned to cut the power in an apparently deserted area. Lou Diamond Phillips (above right, with Sutherland) plays a man named DeSalvo who has some answers. ER Pearl, 8.30pm To make up for the time he took off to care for his mother, Benton (Eriq La Salle) works 48 hours straight, which worries Dr Hicks (CCH Pounder) and has serious repercussions for Benton's mother. It also affects Carter (Noah Wyle), when Benton becomes even more demanding than normal. Greene's (Anthony Edwards) personal problems go from bad to worse when his wife, Jennifer (Christine Harnoss), tells him she may be falling out of love with him.