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The Rookie will play host to another, albeit more specialized, Castle reunion when Annie Wersching pops up on the ABC procedural.

On Castle, Wersching — now a star of Marvel’s Runaways — had a short arc as Kelly Nieman, a prison doc/plastic surgeon who became infatuated with inmate Jerry Tyson (aka the serial killer known as 3XK) and went on to serve as his accomplice and lover.

Now, similarly, Wersching will guest-star on The Rookie as Rosalind Dyer, a serial killer on death row who takes a special interest in Nathan Fillion’s Officer John Nolan.

Wersching’s casting comes not long after The Rookie, as part of ABC’s “Casts From the Past” theme week, had Fillion’s Castle castmates Seamus Dever and Jon Huertas put in cameos.

In addition to Runaways (where she plays PRIDE member Leslie Dean) and her Castle arc, Wersching’s TV credits include Bosch, Timeless, The Vampire Diaries, 24 (#ReneeGoneTooSoon) and General Hospital.

The Rookie, which just got a full Season 2 order, airs Sundays at 10/9c.

Want more scoop on The Rookie, or for any other show? Email InsideLine@tvline.com and your question may be answered via Matt’s Inside Line.