Lock In is a science fiction police procedural novel by American writer John Scalzi.

Further Integrator-Haden related murders occur, making the case larger than expected, and as Shane and Vann dig deeper, they uncover a plot to completely shake up the Haden economy.

Lock In is accompanied by a novella, Unlocked: An Oral History of Haden's Syndrome, an epistolary work which provides background details about the origins of the epidemic.

The Milwaukee Journal Sentinel called it "compulsively readable", and praised Scalzi for having "a combination of skill, vision and intuition.

"[7] An analysis at io9 suggested that, if not for the Sad Puppies ballot-manipulation campaign, Lock In would have been a finalist for the 2015 Hugo Award for Best Novel.