Castle type TV Show network ABC genre Crime

3XK has booked a return trip to haunt Castle and Beckett.

Michael Mosley has signed on to reprise his role as the famed serial killer during Castle‘s big two-part episode in February, EW has learned exclusively.

Mosley first appeared in the series’ third season as Jerry Tyson, who essentially tricked Castle (Nathan Fillion) and Beckett (Stana Katic) into getting him out of jail. He also framed Castle for murder in season five, after which the titular writer inadvertently helped Tyson fake his death.

Unsurprisingly, 3XK returns in the same episodes as Dr. Kelly Nieman (Annie Wersching), a plastic surgeon and an apparent disciple of Tyson’s who cosmetically altered Esposito (Jon Huertas) and Lanie (Tamala Jones) lookalikes that were used to destroy evidence of Tyson’s crimes in the season 6 episode “Disciple.”

“There’s a murder that our cops are investigating at the beginning of the episode that seems to connect to [Dr. Nieman],” showrunner David Amann says of the two-parter. “That puts us on what we think is going to be a fun, dramatic journey for the audience as we try to solve that murder and figure out what her involvement is in it, if any.”

Castle airs Mondays at 10 p.m. ET on ABC.