Arye Gross

Arye Gross will guest-star in the upcoming season of Fringe, TVGuide.com has learned exclusively.

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Gross — whose TV credits include Castle, The Riches and Medium — plays Malcolm Truss, a middle-aged scientist who enters the Fringe fold in Episode 5. Here's hoping he can help solve the mystery of what happened to Peter (Joshua Jackson)!

Fringe returns Friday, Sept. 23 at 9/8c on Fox.

Check out a new teaser for the season premiere: