Sleep, Elizabeth Primrose discovers, does more than refresh the body and clear the mind. Sleep offers protection against something terrible.

Elizabeth knows this too well. A savage attack has left her boyfriend, Bruce, unable to sleep. To induce it, medication after medication is attempted, but all fail to relieve Bruce's suffering-and Elizabeth begins to see a gradual change in the man she loves.

A subtle atmosphere of wrongness now surrounds Bruce-wrongness that affects all who encounter him and grows with every night he cannot rest. Bruce is slowly diminishing-and something else is taking his place.

In desperation, Elizabeth seeks assistance from a mysterious doctor and his shadowy, heavily guarded "hospital." It's a decision that will have consequences she cannot predict. Bruce's inability to sleep opens the door to madness and horror-and leaves Elizabeth desperately defending her actions to an unforgiving jury of her peers.

From the author of Jersey Darm, Circadian explores the darkness lurking on the periphery of reality, waiting for any opportunity to enter the human mind. Bruce may be insane. He may be possessed. Either way, he's becoming something different from what he was-all because sleep has ceased to be an option.