The Halflife

Oblivious to its real purpose, writer Tim Monahan takes the bait of $500 to participate in a ``creativity study'' as this medical thriller unfolds. Tim has doubts after finding himself in a deserted hospital wing, where he learns there will be ``invasive procedures'' as part of the study. He has fewer doubts about Jody Henson, a pretty psychologist working for study director Dr. Barkley, and he delays his impulse to leave. Meanwhile, Maureen, the medium, and Beth, the multiple personality, sense evil in their midst. As it happens, a psychopath known as ``Jonathan'' is stalking female prey near the hospital, so imagine the surprise of Tim and Maureen when an entity named ``Jonathan'' works his way into their writing. This worries Dr. Barkley, who is working for the CIA, and who had surreptitiously implanted ``Jonathans'' into the minds of the participants when they were kids in a plot to create CIA ``super agents.'' Unfortunately, one of them has grown up to be a killer, and Barkley wants to know who it is. So will readers drawn to Gothic sets, disturbing experiments and mental illness. However, a strong ending is not adequate reward for the suspension of disbelief Webb ( Pestis 18 ) requires. (Sept.)