DCI Barnaby and DS Jones investigate the apparent murder of Emily Harte who was run off the road by a car while cycling late at night. The evidence at the scene also suggests that the driver then backed up over her to make sure the job was done. She was a member of the local cycling club and was in a relationship with George Jeffers a professor at the local college. Barnaby quickly concludes that Jeffers was the driver's intended target. Jeffers had several people who might want to get at him. His ex-wife Melanie felt that she was losing her son as he too was spending more time with his father and Emily. Then there's a disagreement with a local technology firm that has built a new air traffic control system built on his theories. Jeffers thinks there a serious flaw and has threatened to go public and the company's CEO Clinton Finn has already taken steps to get the college on his side by endowing a new research building...