The captain of an early U-boat, based in Kiel, receives a telegram instructing him to wait for his crew, the bear cubs Clara and Dmitri, and sail to a rendezvous in the Mid-Atlantic. Clara and Dmitri also receive a telegram: they need to travel back in time and join the U-boat captain in Kiel. Meanwhile on the other side of the Atlantic, a mysterious stranger makes a strange proposal to the captain of the brig Amazon. But the best-laid plans of mice and men oft go astray!