When i first watched this episode it confused the heck out of me. A mysterious corpsman named Mallory, evil Captain Cranes and lots psychedelic lights and shifting between dimensions!
The action kicks off with the reactor running wild...again (just what do they do to it?) Patterson and Kowalski are trying to sort the problem, they ask for help over the intercom but then they are quickly knocked unconscious by an explosion from the reactor.
Captain Crane rushes in to try and push the "control rods" back in (not wearing any suit naturally) he ends up getting thrown about and winds up in sick bay in a mysterious coma.
While they are discussing his condition we notice a rather odd corpsman messing about with a whacking great piece of equipment. As soon as the coast is clear the corpsman named Mallory starts causing chaos with his machine. Another Captain Crane rises up from the originals unconscious body and walks out of sick bay. Conveniently located outside sick bay there is an arms locker, even more conveniently it's not locked! (very reassuring to know fire arms can be taken by anyone, oh and there always kept loaded!) Now with the famous Voyage side arm in hand he strolls down the corridor and enters Admiral Nelsons cabin.
Nelsons pleased reaction to seeing Crane quickly turns to alarm when he notices he's got a fire arm. Crane tells him he's got to die and that he's a stumbling block that's got to be "removed" (this could well have been true! Nelson was always taking over command of the Seaview when Crane was supposed to be in charge, bit of black humour that Crane thinks Nelson has spoilt his career) without further messing about Crane shoots and kills Nelson!
What follows for the rest of the episode is as interesting as it is bizarre! Basically the corpsman Mallory is using his new machine to experiment on the crew. He has found some way of tapping into the "4th dimension" When the evil Crane returns to the unconscious Cranes body we learn that Mallory has somehow isolated sick bay from the events that have just taken place. The murder of Nelson hasn't happened yet. The action then shifts between different dimensions as the evil Crane runs wild and commits more murders! Then the real Confused Crane runs the gauntlet as the crew are out for his hide as he murdered the Admiral and to make matters worse he even interrupts the burial at sea service with a lot of shouting! (good to see the conning tower and deck set dusted off and used)
The action ends up on some weird floating tropical island in the 4th dimension, all the crew are whisked off of Seaview and onto it. Poor Captain Cane now how has TWO evil twins to deal with!! One is even more bonkers and runs around with a maniac laugh.
Luckily the Chief after being confused by it all has finally thrown in and is helping the real skipper.
After much running round the jungle and dodging Chip Morton,Kowalski and Patterson as well the evil Cranes they make it back to Seaview in the flying sub.
Crane spoils Mallory's day when he throws a good old fashion voyage sticker grenade at his 4th dimension machine.....destroying it and sending Mallory goodness knows where!!
I like this episode despite the season four rushed feel and one or two plot holes.
The whole 4th dimension aspect is fascinating, it introduces us to the idea of parallel time lines and that in another existence Captain Crane could have been a cold blooded murderer.
Spoilers are the character of Mallory, just who was he? Crane asked him more than once and he just told him that wasn't important. Writers let off! The part was played totally bland so its difficult to judge. How did he manage to build his machine on a floating island?! And why the hell go to all the trouble of using the Seaview crew as guinea pigs? He could of used anyone? He talked like he wasn't human...was he?
The end was far too rushed (typical season four) with Nelson offering no real explanation other than a totally feeble comment about Mallory being "a little mad" talk about understatement