Seaview is on the lookout for an enemy sub and its underwater sub-pen. Sonar picks up a contact. The rogue sub fires at Seaview, which is saved only by virtue of her new electronic hull shield. Not so fortunate is Captain Crane, who has just located the sub-pen while on patrol in the FS-1. A powerful laser fires a beam at the Flying Sub, crippling the ship. Running out of air, moving in and out of consciousness, Crane is unable to give the pen's coordinates to Nelson. Thanks to the hard work of some enemy agents aboard, Seaview seems unable to rescue the Captain. Worried about Crane trapped in the Flying Sub, Admiral Nelson is particularly impatient in this episode. He constantly barks at Morton and the Chief. One of the enemy agents, Marco, a crewman we have seen in many other episodes, is never found out, and apparently keeps his job on Seaview! (thetvdb.com)