Diagnosis Murder: A Twist of the Knife: Dr Sloan suspects that his flame of long ago, famous heart surgeon Dr Rachel Walters, has murdered US Senator Cabot on the occasion of a guest operation at the community hospital. After a long investigation, Sloan and fellow detectives Dr Bentley and Dr Parker discover her motive: Years ago, Cabot had caused a hit-and-run accident that put her daughter into coma. But how did Dr Walters manage to pass the deadly bacteria on to the senator in front of TV cameras?