Mary Elizabeth Mastrantonio (Law & Order: Criminal Intent) will guest star in the season finale of Grimm. TVLine reports that the Academy Award Nominee will play the "Woman in Black." The finale will air on May 18 and will not be the end for Grimm, which will return next fall for a second season.
The season finale of ABC's Castle has also found a star to secure its rating during sweeps month. TVLine confirms that Tahmoh Penikett (Battlestar Galactica, Dollhouse) will star in the finale in a role that might be recurring. No detail has yet emerged on what the character will be up to, but his leaked profile suggests he will be up to no good. Castle will wrap up its fourth season on May 7.
