The 10th season of this supernatural series begins with Dean (Jensen Ackles) enjoying life as a demon with Crowley (Mark A. Sheppard). However, Dean grows more aggressive when the Mark of Cain is not fed. Meanwhile, Sam (Jared Padalecki), oblivious to his brother's state, is desperately searching for him and, upon learning his fate, attempts to return him to human form. Additionally, the brothers continue hunting supernatural beings and face the goddess Calliope when she brutally forces a school to perform a musical about the brothers' lives. Also, they become murder suspects while investigating a shape shifter and take on an old foe who resurfaces. Elsewhere, Castiel (Misha Collins) is on the verge of death, but does not want to be saved by evil means. This leaves Hannah (Erica Carroll) in a quandary as she tries to help him.