“The Sinner: Season 4” Nonetheless reeling from the trauma of an earlier case a yr in the past, the now-retired Harry Ambrose travels to Hanover Island in northern Maine for a recuperative getaway along with his accomplice Sonya, however, when a sudden tragedy happens involving Percy Muldoon, the daughter of an outstanding island household, Ambrose is recruited to assist the investigation, solely to be thrown right into a thriller of mounting paranoia that can flip this sleepy vacationer island, and Ambrose’s life, the other way up.