The Six Million Dollar Man S04E20 - U-509

When a sub is seen off the coast. It appears to be an old German U-Boat from World War II. A message is sent saying that unless their demands are met, they will kill thousands of people. They agree to a meeting and Steve is sent to meet with the person. The person claims that the sub has a cache of nerve gas which when released and depending on the wind will reach a populated area. Oscar decides to send Steve to get into the sub and to try and neutralize the threat. But Steve is captured and is shown the nerve gas.