“Under the Lake” is episode three of season nine of the new Doctor Who.
This episode starts in 2119 in an underwater base in a flooded lake near Caithness in Scotland. The base is there to drill for oil, but they’ve found what appears to be a spacecraft. Shortly after bringing it on board, the commander of the base is killed and he joins another figure – and they both appear to be ghosts.
Three days later the Doctor and Clara turn up. The surviving members of the crew are trapped on the base, and the ghosts seem hostile – as they try to kill Clara and the Doctor. The ghosts waited until they’d seen the spacecraft before trying to kill them though. After rejecting the idea initially, the Doctor decides that they are actually ghosts – but why are they around.
There’s a nice scene where the Doctor has some prompt cards to help him react properly to a bad situation – Capaldi’s Doctor is rather lacking in empathy, and these are supposed to help. He also clearly need a little more help; you aren’t supposed to read out the either/or options on them.
A cliffhanger ending and the story continues in the next episode, “Before the Flood”.