Big Brother / 8:00pm (13) You probably know the drill by now — and if you don’t, the newest “housemates” surely do. In this two-hour season premiere, they enter the Big Brother House, isolating them from everyone else except host Julie Chen. Alliances will be made and betrayals will be committed. OK, we’re just guessing at that ... but it’s a pretty educated guess, based on earlier rounds of the contest. As usual, the show will be broadcast thrice weekly (also on Thursdays and Sundays).
Modern Family / 9:00pm (7) Martin Short guest stars in “Blindsided” as a veteran marketer who conveys his professional theories to promotions novice Haley (Sarah Hyland). Luke and Manny’s (Nolan Gould, Rico Rodriguez) competition to become senior-class president prompts a rivalry between their families. Cam (Eric Stonestreet) takes action to ensure that his star football player won’t have to leave the area. Ed O’Neill, Julie Bowen and Jesse Tyler Ferguson also star.
This Is Us / 10:00pm (4) Moving back in time again, “The Game Plan” — which reveals the history behind the family’s passionate support of the Pittsburgh Steelers — finds then-childless Jack and Rebecca (Milo Ventimiglia, Mandy Moore) debating starting a family. Kevin (Justin Hartley), meanwhile, discovers that the script for his part in the play is relevant to his own life.
Broadchurch / 10:00pm (BBC) Detective Inspector Alec Hardy (David Tennant) and Detective Sgt. Ellie Miller (Olivia Colman) return with a new case as this acclaimed mystery trilogy opens its third and final season. The pair respond to a call from Trish Winterman (Julie Hesmondhaigh), who reports that she has been sexually assaulted. A rape exam confirms her claim, but the questions of where, when and by whom she was attacked remain unclear.