"A longshanked rascal with a mighty nose!"An intrepid investigative journalist, Sarah Jane Smith, infiltrates a secret research centre where a number of top scientists are being held in protective custody while UNIT investigates the disappearance of some of their colleagues.The Doctor follows the trail back to The Middle Ages in the TARDIS; unbeknownst to him, Sarah Jane has stowed away on board. It seems that a robber baron called Irongron has made a deal with Linx, a Sontaran of the Sontaran Army Space Corps. Linx gives Irongron advanced weapons in exchange for time and shelter while repairing his damaged spacecraft. The kidnapped scientists are working under hypnosis to help.The Doctor helps local lord Sir Edward of Wessex to repel an attack by Irongron's men, then drugs the food in Irongron's castle in order to remove the advanced weapons while they sleep. With the help of one of the scientists, the Doctor then sends the scientists back to the 20th century.Linx kills Irongron and is about to leave when he is shot in the back of the neck with an arrow by Hal, one of Wessex's archers. Turns out that's the only weak spot on a Sontaran's armour - the "probic vent" - and he dies. The Doctor, Sarah and Hal escape before the ship can explode and destroy Irongron's castle.
— Irongron describes the Doctor
An official BBC radio play by Barry Letts, "The Paradise of Death", takes place between this episode and the next and stars Three, Sarah Jane and the Brigadier.
- Achilles' Heel: The Sontaran's probic vent.
- Anachronism Stew: It's implied that the action may be taking place pre-1066 ("Wessex," as a place name, was quickly dispensed with after the Norman Conquest), but the armor and weapons look to be anywhere between the 13 to 15th centuries. Plus peeling potatoes!
- Blasting It out of Their Hands: Once by Linx with his hand laser, and more impressively, Hal shooting a sword out of Irongron's hand with a bow.
- Blind Without 'Em: Prof. Rubeish. He fashions himself a monocle using Linx's equipment.
- Bullet-Proof Fashion Plate: After spending days in the middle ages, exercising (and presumably sweating) and rolling around in the dirt and straw, the Doctor's clothing is still immaculate.
- Call Forward/Call Back: The Doctor remembers the last time he met a Sontaran, but the actual events behind the meeting wouldn't be shown on TV for another 20 years.
- Chandelier Swing: The Doctor does one during a fight with Irongron's men.
- Cut His Heart Out with a Spoon:Irongron: I'll chop him up so fine, not even a sparrow will fill its beak!
- Enhanced on DVD: The special release adds a starburst glow and laser blast effect to the orange tip of Linx's Sontaran hand laser device that makes it more apparent when it's activating, and replaces the exterior shot of an explosion going off that implies the castle Irongron sacked blew up (the series didn't have the budget or technology back then to show a castle properly explode) with a CGI effect where it is actually shown to be blown apart as everyone runs for cover.
- Evolving Credits: This episode debuts the opening sequence used until Three's finale, when it was modified to become Tom Baker's intro for all but his final season.
- Fish Out of Temporal Water: Sarah Jane.
- Getting Crap Past the Radar: When the Doctor says he has to go find a young girl (Sarah Jane), Prof. Rubeish says to himself: "Young girl? Should have thought he was a bit old for that sort of thing."
- Going for the Big Scoop: Sarah Jane.
- Imperial Stormtrooper Marksmanship Academy: The knaves of Irongron, and Irongron himself, can't hit anything with their new 'star weapons'. Doesn't really discourage them from having fun with them, if a bit frustrating when actually in battle. Justified as older rifles weren't very accurate and the men firing them had normally fought with medieval weapons and had never seen a gun before. They decide to kill the Doctor via firing squad as aiming practice.Irongrad: [amused] These knaves of mine aim so ill, Doctor, you are mayhap safer to stand still.
- Improbable Aiming Skills: Hal the archer can put an arrow through a probic vent from quite a ways away.
- I Need a Freaking Drink: A caffeine variation; when the Doctor reveals to Sarah Jane that he is an alien time-traveler, after a moment's shock she announces, "I could murder a cuppa tea!"
- Informed Ability: The Doctor's 'skilled' swordplay.
- Instant Sedation: Inverted. The drugged food takes a minute or so to knock out the people who ate it, but they are awakened with just a shake and a warning the castle is going to blow up.
- Intrepid Reporter: Sarah Jane.
- Laughably Evil: Irongron and Bloodaxe are a damn goofy couple of guys.
- Magic from Technology: Both Linx and the Doctor are seen as wizards by the locals.
- May-December Romance: Rubeish mistakes the Doctor's interest in Sarah as this. Probably because he's eccentric, a bit of a distracted klutz, and prone to letting his thoughts meander into La La Land.
- The Middle Ages: Sarah Jane seems to think it's The Dung Ages.
- Mind Control: Linx does this to the scientists.
- People in Rubber Suits: Linx.
- Pull the Thread: The Doctor, when he sees through Sarah Jane's cover story
- Scullery Maid: Sarah Jane poses as one to infiltrate Irongron's castle and drug the food.
- Slipping a Mickey: Sarah Jane drugs Irongron's men's food and drink.
- Unfortunate Names: Professor Rubeish's name sounds like "Rubbish". The Doctor almost thinks he's been insulted when the professor first introduces himself.
- Unwanted Rescue: When the Doctor finds Rubeish at the castle, the scientist doesn't want to be rescued because he's too interested in the work being carried out for Linx. Also, he's so nearsighted and so naive that he hasn't actually realized how much danger he's in.
- Wayback Trip/Giving Radio to the Romans: In this case, keeping firearms from developing centuries too early.
- Wham Serial: This serial names the Doctor's home planet, introduces one of the most popular companions of the series, Sarah Jane Smith, and also introduces recurring enemy race the Sontarans (although the Second Doctor will later have previously battled them).
- Where's the Fun in That?:
- After the Doctor tells the Brigadier that he'll go search for the missing Professor Rubeish in the TARDIS, he pretty much says this to the Brigadier after the Brigadier points out the TARDIS's not-quite-good landing record.The Doctor: A straight line may be the shortest distance between two points, but it is by no means the most interesting.
- The Doctor pretty much states his MO when Sarah Jane Smith asks "Are you serious?"The Doctor: About what I do, yes. Not necessarily about the way I do it.
- This is Irongron's reaction when he gets a firing squad of his men to kill the Doctor with their new rifles, and Linx tells him to let him (Linx) do it personally.Linx: Give me a weapon. I will destroy him.
Irongron: Come now, Linx. Would you spoil good sport?
- After the Doctor tells the Brigadier that he'll go search for the missing Professor Rubeish in the TARDIS, he pretty much says this to the Brigadier after the Brigadier points out the TARDIS's not-quite-good landing record.
- Worthy Opponent:
- Irongron briefly considers the Doctor as this, appreciating his wit as he dodges the bullets of the firing squad.Irongron: Beshrew me, I grow fond of this Doctor.
- Subverted with Irongron and Linx. They work to each other's mutual gain and occasionally exchange respect and good natured banter but in their time apart, they express entirely justified distrust and constantly plot to murder each other.
- Irongron briefly considers the Doctor as this, appreciating his wit as he dodges the bullets of the firing squad.
- Wrong Genre Savvy: See The Middle Ages above.
- Ye Olde Butcherede Englishe: When Sarah Jane starts speaking like this, Irongron's maid thinks she's nobility.