Stalker will take on an Original new case this Wednesday (CBS, 10/9c) when Phoebe Tonkin guest-stars as one of the episode’s victims.

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In the exclusive sneak peek above, Tonkin plays a lifeguard who’s being terrorized by a mysterious stalker. As she and her fiancee (Jane the Virgin‘s Michael Rady) brainstorm who could be behind the attacks, Tonkin pinpoints her character’s ex as a possible suspect.

Intimidating? Possessive? He totally sounds the type.

Unfortunately, it’s going to take a lot more detective work to track down the real culprit — but time isn’t on Tonkin’s side.

Press PLAY on the video above for a sneak peek at the episode, then hit the comments with your thoughts!