When Tom and Wilma Weston stepped aboard the cruise ship, Sea King, they were unaware that they were embarking on the adventure of a lifetime. Tom, a retired Coast Guard captain, was aware that gateways to parallel worlds had been discovered, so he understood what happened when a bank of mist appeared on the surface of the sea. He was surprised when an early 19th century warship flying a British flag came out of it. Being acquainted with the captain of the cruise ship, he was willing to board a lifeboat and approach the ship to let its captain know how he could return to his own world. As a result, he rescued a British sailor who had been condemned to death for sleeping on watch and recovered his girlfriend who jumped into the sea when she saw the rescue.
When gates start opening randomly, warships from a worls that had destroyed itself with nuclear and biological weapon appear bringing terror on the high seas.