The background is briskly sketched in: scenes of Moscow, a missile being prepared for launch, a busy Control Room, a group of men in the Kremlin attentively watching the proceedings on a televison set. The group is headed by Sgt. Shultz (er, the Chairman). The launch is sucessful, and we learn that it is carrying a satellite. One of the men, toasting their sucess, mentions the date; May 27, 1973. A telephone call interrupts the celebration, and the man who answers shouts to have the rocket destroyed immediately. Can't be done. The control system and the abort system have both malfunctioned, and it's going to fall to Earth. The man whispers in the Chairman's ear. The Chairman looks stunned, but he knows his duty. Marching across the hall, he enters a small chamber and picks up...the Hot Line.
At the White House, the corresponding odd-shaped telephone is flashing and buzzing in the Oval Office. Scotty (er, the aide; we'll learn in the episode "Hail to the Chief" that his name is Larry Tobin) answers. You can see why he's an aide; he wastes no time asking questions the Chairman won't answer. Awakening the President, he announces the call from the Hot Line (no further description needed) and arranges for a National Security Council meeting to be assembled immediately. The President hastens in.
On the Seaview, it quickly becomes clear that Nelson, at least, has been partially informed of what's going on. He consults a map, and asks Crane how quickly they can reach certain coordinates. It's only 15 minutes away. They're going to rendezvous with a ship. Crane is startled; they've been monitoring said ship--it's a Russian trawler. But you don't argue with orders from the White House. The trawler is actually a tracking station. Gregory Malinoff, Technician First Class, Order of Lenin, comes aboard, accompanied by Crane and Kowalski. A second technician, Gronski, is flying in from Moscow; he's to be picked up in Santa Barbara. Kowalski is amazed at having a Russian on board. Later in the series, we'll find that he speaks Russian, but there's no indication of it here.
Back at the White House, the aide reports that all attempts to destroy the satellite have failed; they've also confirmed that the malfunctions were due to domestic sabotage. (This gives you an idea of the current political climate; under other circumstances they might try to blame someone else.) The impact point is estimated to be 200 miles off the California coast. The satellite's nuclear reactor will reach critical mass shortly after impact, and, if not deactivated, the resulting explosion could destroy San Francisco and half a million people. Lethal fallout precludes the option of shooting it down, and there's no time for a safe evacuation. The President announces that he's ordered Nelson to get in there and deactivate the thing (as if we hadn't guessed that already.) At the airport in Los Angelos, Technician Gronski arrives, a small, rather elderly man, quite the physical opposite of the tall, muscular Malinoff. There's an elaborate scene in which two uniformed men steal an airport cart, fetch Gronski from the plane, kill him, and replace him with a man of similar appearance. I can't imagine why they gave it away like that. They should have substituted a scene from Russia with a small group of men announcing with satisfaction that "their agent" had sucessfully switched places with the real technician, and left us watching carefully for clues to whom it might be. The intimidating Michael Ansara would have been a splendid suspect.
"Gronski" comes on board the Seaview. He and Malinoff had never met, though they of course know of each other. "Gronski" addresses Malinoff in Russian, which seems rather rude in front of the others. Nelson informs them that calculations now indicate that the satellite will land closer than estimated. Malinoff seems incredulous, but the data was sent from the Kremlin and has been verified. The deactivation will have to take place under water--and Malinoff confesses that he does not know how to scuba dive. "Gronski" chews him out in Russian, then says that they must abandon the plan. (And do what?) Nelson asserts that they can teach Malinoff how to dive, as long as he can swim. (Malinoff doesn't actually say that he can or can't.) More data arrives from the White House, which Nelson checks over. The impact will be less than 50 miles from San Francisco--and will take place two hours earlier.
Down in the Missile Room, Kowalski indicates that the scuttlebutt is already running wild. He says that one of the Russian rockets goofed up--which is true enough. Crewman Clark and the others are amused, but Clark's amusement fades as 'Ski goes on to say that the capsule is loaded with atom bombs and will land right on San Francisco. (This is a fairly realistic distortion of the facts, just the way you would expect a rumor to grow.) Clark, looking very apprehensive, darts out of the room. He runs into Crane--just the man he's looking for--and asks to send a radio message to his family in San Francisco. Crane, rather brusquely (he's going to regret it) tells Clark that they're on radio silence, and sends him on his way. Up in the nose, the scientists are conferring. Malinoff says that the figures don't add up--unless the rocket was tampered with. When Nelson tells him that it was, Malinoff takes it as a joke. The technicians had only been told that the malfunctions were an accident. After conferring between themselves, the technicians announce that critical mass will be reached in 5 hours--and it will take two and a half hours to disarm the thing. Seaview will not even get there for another three hours--meaning they will be half an hour too late. Malinoff thinks that they can cut the time, but only a little. Nelson orders full emergency power, ignoring the safety limits. This is the hardest the Seaview has ever been pushed. (This would have been a good time for those Strontium 90 pellets from a few episodes back.) It's now time to inform the crew just what is going on. Crane makes a shipboard announcement--sounding just like a news broadcaster. Clark and Kowalski are in one of the crew's quarters. Clark is frantic; his wife and child are in San Francisco. Kowalski's reaction is very obnoxious, a lot different from the Kowalski we would see in later seasons (or even later in this one). He asks Clark, "What makes you so special?" completely disregarding that Clark had just told them why he was especially anxious! Clark dives at Kowalski, but the fight is broken up by Curley before it's even well begun. Chip Morton, who apparently just happened to be passing by, assumes that Kowalski is at fault. (They know him.)
Seaview surfaces to observe the splashdown, which takes place at night. It's a nice shot, although it looks a bit cartoony. Seaview quickly heads for the impact point. Gronski, who has a brief philosophical exchange with Nelson, tells Malinoff that he may know a way to cut the disarming time (in addition to Malinoff's method?) Seaview makes metal contact, and Gronski and Malinoff go to suit up. Malinoff is making his first dive at 400 feet, and Nelson allows them to go out with no supervision, which is utterly ludicrous. Having an additional diver to keep an eye on Malinoff (and watch for predators) would not have harmed the plot in the least. As Seaview makes her final approach, Clark quietly slips into the radioshack (which here is in a curtained-off area). He asks Sparks to send a message for him, but Sparks, irritated, tells him to shove off. Clark makes a grab for the radio. Curley (who seems to have an instinct for spotting trouble before it starts) is immediately on hand to grab Clark, quickly followed by Crane. Curley's ready to put Clark in the brig, but Crane asks Clark for an explanation. Understanding Clark's fears, Crane does not arrest him--this time--but points out that the panic arising from a warning could kill thousands of people, including Clark's family. Curley quietly points out that a number of men have family in the Bay Area, and Crane orders a guard posted at the radioshack.
Seaview parks on the bottom and the two technicians go out. Nelson opens a link to Washington. There is a fairly lengthy swimming shot before they reach the capule and circle it. The side with the hatch is pressed into the seabed; they will have to cut open the capsule--which could trigger the explosion. The techs start discussing the situation in Russian, no doubt frustrating Nelson and Crane no end. Washington is in touch with the Kremlin; all they can do is stand around and sweat. Nelson is concerned about Malinoff (but not enough to have sent a diver out with him!). Crane mentions that Malinoff had been having trouble clearing his mask during practice--a common problem with novice divers. This would seem to foreshadow a complication, but it doesn't--it just provides Nelson an excuse to blow a little steam. There are scenes of nervous crewmen standing by as the minutes tick by. "Gronski" finally pulls out a long cylinder, and Malinoff gestures triumphantly. "Gronski" makes some final adjustments, and Malinoff playfully reaches out and bops him on the head, which seems a little out of character, but it's been a tense couple of hours. Malinoff announces over the radio that they have finished. As they swim back to the Seaview (quite a long swim, why didn't they park closer?) Malinoff suddenly slows, pressing a hand to his side. "Gronski" can't seem to make up his mind whether to help him or not--first he takes hold of him, then swims ahead, then comes back again. Coming back inside, Malinoff steps out of the escape hatch and right down to the floor. Curley wonders if it's the bends (which occurs when you suddenly ascend from a deep level, so it wouldn't apply here). There's no explanation of just what was wrong with Malinoff, and he seems to recover quickly. Curley informs Nelson and Crane that the men are back. Crane reacts delightedly, as though he hadn't already heard Malinoff report on their sucess. They're 35 minutes ahead of schedule. Nelson starts to call Washington, but the President beats him to it. Nelson starts to speak, and breaks off in mid-sentence. Crane instantly knows something's wrong. Russian Intelligence had captured one of the saboteur ringleaders. They have reason to believe that one of the technicians is an imposter--but the ringleader died before he could say which one.
They have just half an hour to expose the imposter, learn what he did--or didn't do--to the satellite, and disarm it. Nelson has Crane summon the techs to the nose--without saying anything--and arranges with Sparks to call him in 5 minutes with a coded call from Washington (ignoring whatever Nelson says) and to have the Master-at-Arms standing by. The technicians arrive. This could have been a much more exciting scene if we hadn't already known about "Gronski", but it goes over pretty well. Nelson calls for a celebration, asking Crane to do the honors with the booze. Crane (who perhaps can't act as casually as Nelson) doesn't ask the men what their preference is--he just grabs a bottle and pours. (Whiskey, perhaps--it's dark colored.) "Gronski" is in a hurry to get back to Moscow. Nelson says that they will put up a marker before leaving the area. A call comes in; Nelson answers. Nelson seems to be speaking with the President; new orders are coming in. Crane watches the men closely. Malinoff looks indifferent, "Gronski" is frowning. Nelson tells Sparks to have Morton secure the navigational watch--they'll be staying a while. The Kremlin had asked that they salvage the electronic brain. "Gronski" is startled, but Malinoff is agreeable. Nelson decides to wait and make the dive the following morning. "Gronski" points out that the brain is damaged and worthless, but Malinoff counters that it's not their place to question the Kremlin--there must be a good reason for it. Nelson dryly notes that "Gronski" seems upset, and Malinoff wonders if he's ill. "Gronski" gets agitated, tells Crane that they have to get away NOW--and finally confesses that he recapped the fuse and reconnected some wires. Malinoff instantly offers to assist Nelson, who flatly states that he would not survive. This is an irritating statement, considering that no one seems to know just what happened to Malinoff in the first place. "Gronski is led off, yelling that it's too late--they only have ten minutes. (They seem to have dithered around for a good twenty-five minutes). In ten minutes time Nelson gets down to the Missile Room, gets suited up, exits the sub (looking like Crane thanks to stock footage) swims out to the capsule (ALONE!), sets off a short in the wiring, traces the short, deals with it and saves the day. What a guy.
After Nelson reports that he's on his way back, Crane opens the intercom to the whole ship, so that they can hear his report to the President. All is well. Later, in the nose, Malinoff, Morton, Crane and Nelson assemble for a champagne toast. Malinoff confesses that he likes it better than vodka. He also comments that he had thought that they had too many luxuries on the Seaview (would have been interesting if we could have seen some of this reaction) but has now learned to appreciate it. Setting his mischievousness aside, he gravely offers a toast to their homes--wherever they are.