The season 4 opens with a series of dramatic events and issues starting with a discharged naval soldier. Investigations by partners Eric and Nell, who learn more about unknown former soldiers, began. On the other hand, there are four men dying in an explosion in Pasadena, where the four participated in the program of the Bureau of Naval Intelligence and remains the fifth participant, and a man dies in a malicious accident deliberately, and may be the identity of the victim in a candidate for the US Senate.