Bad Medicine — Carolyn Keene

CASE #35
Nancy checks into a hospital where murder is the chief resident

To help a friend, Nancy goes undercover at a River Heights hospital. Trevor Callahan, a young doctor, is being blamed for his future father-in-law's sudden death after heart surgery. But before Nancy can investigate, the body is stolen!

When the teen detective starts work in the emergency room she soon finds every moment is vital. A mysterious killer is stalking the wards, and Nancy is high on the critical list. If she fails to diagnose the clues, her own life will need intensive care -- and chances are the young sleuth won't survive the treatment.