No More Fairy Tales
When they finally manage to free themselves, they stumble on to a spaceship hidden inside the castle. "At last, something real. No more fairy tales," proclaims the Doctor. Accessing the ship's databanks, the Doctor explains to Robin that after crashing, the ship blended in to its environment while trying to repair its engines -- with gold we've seen the sheriff collecting. The ship creating this environment, the evil sheriff, and even Robin, hero of the people, based off of old legends, which he demonstrates by showing Robin the references to his story in he computer -- including a blink-and-you'll-miss-it shot of 2nd Doctor Patrick Troughton portraying the character, a nice nod to classic fans.
Another blink-and-you'll-miss-it moment is a shot of the ship's original destination: The Promised Land, where the robots in the premiere were headed to... and may or may not have wound up when the episode's big bad woke up in a garden with the mysterious Missy, who told him he was in heaven. It's this episode's only link to season 8's overreaching story... but as with Moffat's recent seasons, we're not likely to figure out what's going on until he decides to tell us.
Robin doesn't have much time to question whether he's man or machine as the sheriff barges into confront them. Robin manages to escape with Clara, but the Doctor is knocked out -- and, considering the Doctor's grouchy persona this season, it's surprising we've gotten to episode three before that's happened. When the Doctor wakes to find himself chained up below the castle, he incites a riot, getting the servants to work together and reflect the robots' lasers back at them with serving trays. It's more silliness, but it's effective, allowing them to escape the castle before the ship activates its damaged engines, which the Doctor suspects will cause the ship to blow.
However, the sheriff confronts the Doctor on his way out, giving a typical villainous speech about how he intends to rule England from the skies. This gives enough time for Robin and Clara to make a grand entrance, in which leads to a classic Errol Flynn-style sword fight between Robin and the sheriff, winding up with the two of them fighting on a beam above a vat of molten gold. After the sheriff cuts his arm -- suggesting that Robin is human after all -- Robin then mimics the move the Doctor used to push him into the stream to send the sheriff into the molten gold. That's gotta hurt.
But there's no time to celebrate: the ship is taking off and when it explodes it will take most of England with it. Continuing the episode's farcical tone, the Doctor decides to shoot the ship's engines with the golden arrow to, hopefully, give the ship enough of a boost to get further away before it explodes... which just leads to the Doctor, Robin, and Clara arguing over which one will shoot the arrow. But the three of them finally seem to have come to terms and decide they'll work together to do it since Robin's arm is hurt and the Doctor only used high-tech homing arrows to win the contest earlier.
Surprise! This madness actually works, and the ship makes it to orbit before it explodes, wrapping up the storyline pretty neatly.