Unforgotten from WGBH’s MASTERPIECE continues. Cassie and Sunny are working to track down the killer of a teen. The investigation leads to a tight-knit group of four old school friends whose bonds are put to the test when they find themselves under suspicion. Tonight, Cassie and Sunny finally get closer to some truth about the night Hayley disappeared, and the case takes a devastating turn for Cassie.

Watch it tonight at 9pm on WGBH 2.