The Affair Sundays, 10 p.m., Showtime.

People on TV shows have affairs all the time, although usually in the context of doing other things, like solving crimes or treating patients or operating space stations. On The Affair, the affair is the whole show, and creators Hagai Levi and Sarah Treem (who worked together on HBO’s In Treatment) clearly want their audience to understand how incredibly serious it is that schoolteacher and frustrated writer Noah (Dominic West) and waitress Alison (Ruth Wilson) are getting it on. To that end, the show is full of portentous voiceover (Noah and Alison narrate the same events from different perspectives) and hushed dialogue, with a visual style that favors soft-focus, sun-dappled shots suggesting melancholy and regret.

With the two main characters recounting events at some indeterminate point in the future to a man who appears to be a police officer, The Affair is like the True Detective of relationship dramas, and like HBO’s overrated crime story, it’s ponderous, morose and way too self-important. The cast (including Maura Tierney and Joshua Jackson as the respective spouses) is strong, but the material is sometimes laughably heavy. Never has the rush of a new sexual relationship been such an oppressive bummer.