Nikki escapes the burning building but Petra dies and Leo's examination shows she was injected with anthrax. Jack identifies one of the basement victims,also injected,as being Lucas Ballinger's wife and Nikki surprises him at the scene of the murders though he flees. He goes after Hearns and later Chrissie finds Roper,who was the accomplice in taking the virus out of Ballinger's workplace, dead. The team must locate Ballinger and find out why he allowed his wife to be a victim as well as stopping him from committing a terrible revenge which could endanger thousands of lives. Leo meanwhile successfully gets Shona's conviction overturned.