When the Master makes friends with aquatic lizard men and Britain nearly triggers World War III with torpedoes and terrible decisions.
Short Synopsis
The Doctor and Jo visit a high-security prison where the Master is being held (under surprisingly lax conditions). Meanwhile, reports of strange sea-monsters terrorizing sailors surface. Soon, the Doctor uncovers a new race of Silurians — the Sea Devils — who want their planet back, preferably without humans. Negotiations go… poorly.
Extended Storyline
The Doctor and Jo pop by a fortress prison on a sea fort to check on the Master, who’s supposedly locked up tighter than Fort Knox. In reality, his cell is better furnished than most B&Bs, complete with a library and a record player. Unsurprisingly, the Master is already scheming with his jailers and plotting contact with the Sea Devils, reptilian cousins of the Silurians who live under the waves.
Meanwhile, sailors are vanishing, ships are being sunk, and something scaly keeps surfacing off the English coast. The Doctor, poking around in his velvet cape, finds evidence of the Sea Devils and tries his usual “can’t we all just get along?” speech. They’re not entirely convinced — humanity’s track record with the Silurians wasn’t exactly inspiring.
The Royal Navy, however, doesn’t do diplomacy. Enter lots of stock footage: ships firing guns, helicopters whirring, men in uniform shouting things like “Depth charges away!” as if humanity can solve every problem with enough explosives.
The Master, naturally, stirs the pot, helping the Sea Devils build a device to wipe out humanity. The Doctor tries his best to broker peace, but the humans panic and launch a military assault, the Sea Devils retaliate, and things spiral into all-out war.
In the end, the Doctor sabotages the Sea Devils’ doomsday device, reluctantly leaving them buried beneath the ocean once more. The Master fakes his own death in a hovercraft escape (yes, really), leaving the Doctor looking rather annoyed that humanity and reptiles just can’t stop fighting long enough to avoid another apocalypse.