In the latest In the Line of Duty series, Detectives Earl Solano and Paul Derek scramble to covertly help their friend Kevin Brooks investigate a thirty-year-old case when plans for a top secret military airplane resurface. Brooks, a CIA agent, begins the search upon receiving a request for help from his mother-in-law. Brooks' mother-in-law is shocked to receive a telephone call from her husband, Ezekiel Dade, who asks to see the daughter he has never met. Now out of prison, Dade had been convicted for bank robbery thirty years earlier. Since Brooks' mother-in-law had been questioned by police decades earlier about an alleged Swiss bank account belonging to her husband, she thought Dade must have committed the bank robbery he'd been accused of and would die in prison. Brooks wants to help his mother-in-law pave the way so she can introduce his wife to her father. Brooks' wife does not know that her father is alive or that he had been in prison. As Solano and Derek surreptitiously help their friend investigate the old case, the bigger the mystery gets and the more dangerous it becomes. Both friends and enemies of Dade's reemerge, all attempting to learn The Ezekiel Code.