The Key to Midnight is a novel written by Dean Koontz originally under the name "Leigh Nichols". It was first published in 1979.
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Alex Hunter didn't come to Japan to fall in love. But Joanna is the most beautiful, exciting woman he has ever met. Yet, Joanna is not who she thinks she is. Ten years before, a bizarre experiment recreated her mind. To be free, Alex and Joanna must reopen the door into the nightmare past.