MUM Stream on BritBox. For more on moms (or one, at least), see this British sitcom. Lesley Manville stars as Cathy, a widow who spent the first two seasons grappling with grief, dealing with bumbling family members and heading more and more clearly toward romance with Michael (Peter Mullan), who was a close friend of her deceased husband. The third and final season, which ran overseas earlier in the year and is now available for audiences in the United States to stream on BritBox, changes the way the show handles time: Where the first two seasons each followed Cathy over many months, the third takes place over the course of a single week. The results received some strong reviews from critics in the show’s native country. “Before now, ‘Mum’ probably made you cry once a year,” Jack Seale wrote in a review for The Guardian. “Prepare for that to become three or four times an episode.”