The CBI is put on the case of a triple homicide, where two police officers and the fiancee of an EMT were brutally murdered. The EMT, Todd, is livid about getting revenge for Keeley's murder, and Jane definitely understands that, having lost his family to Red John.
When Jane tries to uncover motive for the woman's murder, he keeps running into dead ends. Todd has an alibi for the night in question, having spent the evening with his fiancee's father, a wheelchair bound veteran. Other leads fall short, but then Todd physically assaults one of the suspects, with Jane trying to talk some sense into him.
The gun used in the murder was also used in two other crimes, and both victims were cops. Perhaps there's a serial cop killer on the loose and Keeley was just in the wrong place at the wrong time.
Meanwhile Ellis Mars, an astrologer, has been trying to help out with the case, and Jane (after being initially dismissive) starts to plant information which aids in Mars's attempts. Later, however, Jane takes Todd to Mars and tells him that Mars is the killer. Todd doesn't know how to react, but he knows that Mars isn't the culprit. With this little test, Jane knows the truth: Todd committed the murders.
Todd is arrested but insists on speaking to Jane while in holding. When Jane arrives, however, Todd has been set on fire. Later, in the hospital, Todd mutters the "Tiger, Tiger" poem to Jane before dying of his injuries. Has Red John struck again?