Not the typical spy murder mystery, Southern Cross is a unique tale of double agents, espionage, revenge, and murder leading investigators from a morgue in Manhattan to the SS Southern Cross, a passenger liner sailing from New York to Cuba. Forced to use limited resources, a doctor from San Francisco and a young Paris police inspector scramble to uncover a vicious murderer before another passenger is killed, and before the ship docks in Havana and five-hundred travelers flood the pier.