Sam is shaken when she has to look into the death of a very dear friend, Dr. Annabelle Evans, a Cambridge professor. She was found in her home, badly beaten in what appears to be a botched burglary attempt. The police immediately focus on the husband as the likely killer but Sam suspects that an altercation at a local restaurant during the May Ball, where a waiter spilled wine on Annabelle and was fired on the spot, may provide another suspect. Sam is also intrigued by the relationship some of her students may have had with Annabelle, particularly when she learns her friend may have had a lover. In her personal life, Sam has moved on. Her sister Wyn has relocated to Ireland and Peter Ross has also been transferred. She does however run into an old friend who also happens to be an acquaintance of her business partner Trevor.

As Sam, et al continue to look into Annabelle's violent murder, another woman is similarly assaulted.

Stephen Harrington, a friend of Leo, is concerned that his daughter Rachel, an aid worker, has gone missing in Zambia. Leo and his colleagues fly to Africa where Rachel's corpse is discovered. It seems that she was investigating the deaths of local villagers and may have been silenced. In the absence of the local coroner, the team get involved but find that uncooperative police officers are not exclusive to Britain.

With another aid worker now dead, the pathologists are trying to piece together just what Rachel was up to. Dr. Andrews tells them that Rachel had been trying to trace the source of an infectious disease that she believed had been affecting many of the local villagers. She had originally believed that the disease was water-borne but all tests had proved negative and was therefore looking at other possible sources. Yet another death however strikes the local ex-pat community. With tensions rising, Nikki finds herself in jail and and Harry getting the cold shoulder from the local coroner.

A prisoner is killed during a riot, Nikki is on hand to investigate the scene, inside The Prison she recognises a face from her past.

As the team investigate a second death, Nikki's theory starts to fall apart. Can she put her fixation with Scott aside and find the killer?