A stuffy dinner party in the home of Harry’s former colleague goes awry when a vomiting bug hits all the guests but Harry. After the cause of the sickness is traced to a dead body in the home’s well, Charlie’s sergeant, Vicky Boyle, leads the investigation. Too eager to prove herself, Vicky makes some rash choices and zeroes in on Harry as the culprit, leaving Fergus to prove her innocence.