The CW released the Official Description of the Episode 5.17 called “99 Problems“, to be aired on April 8.
You can read the official description..
5.17 – “99 Problems” Official Episode Description
MICHAEL SHANKS (“STARGATE SG-1,” “SMALLVILLE”) GUEST STARS AS A HUNTER — Sam (Jared Padalecki) and Dean (Jensen Ackles) are outnumbered by demons, but are saved at the last minute by Rob (guest star Michael Shanks) and his townspeople, who are aware of the Apocalypse, and have been training to fight and kill demons. The small town is very religious and Sam and Dean meet Pastor Gideon (guest star Larry Poindexter), who introduces them to his daughter Leah (guest star Kayla Mae Maloney.), whom he claims is a prophet. Leah tells the townspeople they must obey her orders if they want a spot in Heaven but when she starts turning the townspeople against each other in the name of the Lord, the brothers realize they must kill her.
Charles Beeson directed the episode written by Julie Siege.