Supernatural 12×21 “There’s Something About Mary” Season 12 Episode 21 Sneak Peek – Sam (Jared Padalecki) and Dean (Jensen Ackles) are alarmed when they learn hunters are being killed by suspicious “accidents” all over the country. They decide it is best to find Mary (guest star Samantha Smith) and make sure she’s safe. Meanwhile, Toni (guest star Elizabeth Blackmore) is back in the states and she and Mary face off. PJ Pesce directed the episode written by Brad Buckner & Eugenie Ross-Leming (#1221). Original airdate 5/11/2017.