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Elizabeth Keen isn’t the only FBI agent who’s gone rogue: The Blacklist‘s Donald Ressler is doing some unsanctioned investigating of his own, if our sneak peek at tonight’s episode (NBC, 9/8c) is any indication.

In the exclusive clip embedded above, the typically straight-laced Ressler makes a side project out of tracking down Katarina Rostova (aka Liz’s mother), who he suspects may still be alive. Though Katarina allegedly died by suicide years ago, there’s also been rumors that the woman has merely been in hiding this whole time. (Liz, as you’ll recall, was told that her mother died, and Blacklist viewers haven’t gotten conclusive answers regarding Katarina’s whereabouts.)

Ressler enlists the help of a CIA contact for more dirt on Katarina — but he doesn’t receive nearly as many clues as he’d hoped.

Elsewhere in Episode 16, titled “Lady Luck,” Ressler and Liz will investigate a Blacklister who offers to erase gambling debts — at a deceptively high price. Meanwhile, in an effort to find the individual who turned him in to the police, Red will test the loyalties of his business associates, leading Dembe to grow concerned.

Watch our sneak peek at tonight’s episode above, then drop a comment with your thoughts!