Night Shift by Robin Cook

In this exhilarating new medical thriller by bestselling author Robin Cook, fan favorites Jack and Laurie are lured into the dark underbelly of hospital dangers when an internist dies mysteriously.
Colleagues-turned-spouses Dr. Laurie Montgomery and Dr. Jack Stapleton already have their plates full with demanding forensic pathology work and family pressures. The last thing they need is the sudden death of a colleague. Yet when Laurie's apparently vital and healthy longtime friend Dr. Sue Passero dies mysteriously in the hopsital parking garage, an autopsy is required, and it falls uncomfortably under Laurie's purview as the chief medical examiner. So when Laurie asks Jack to take special care with the case, he can hardly refuse.
With his curiosity sparked by an inconclusive autopsy, the indefatigable Jack is compelled to resolve the case at hand, and sets out to investigate on-site at Manhattan Memorial Hospital, even though it means blatantly defying the Office of Chief Medical Examiner's rules. What started out as an inquiry into Sue's tragic passing soon turns into a deadly and dangerous chess game between Jack and the clever and deranged killer, who might just administer another lethal blow if Jack isn't careful.