CSI: Crime Scene Investigation will start season 15 off with a blast from the past - Russell's past that is.

CSI: Las Vegas' Romance In Store For Russell & Finlay? Past Spills Out With Mark-Paul Gosselaar's Serial Killer Case

D.B. Russell locked away the Gig Harbor killer years ago, but a mysterious phone call will make him doubt his work during "The CSI Effect."

The Las Vegas team will be in for double trouble when Franklin & Bash's Mark-Paul Gosselaar takes on the roles of Jared Briscoe and Paul Wintrhop - the alleged Gig Harbor killer and his mysterious twin brother. Separated at birth, the appearance of this new twin and a copycat killer will complicate the fate of the original alleged killer.

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Don't expect the problem to be solved anytime soon, however.

"Hey, did you guys want to do a season-long killer this year?" the CSI Writers' Room asked in early June, teasing Gosselaar's continuing role.

In the meantime, Finlay will have her own issues - particularly a mysterious car bomb.

Find out more when CSI: Las Vegas returns to CBS for a 15 th season this fall. Click the video below to see a preview from the series latest episode.