While having a sulk on a human colony in the far future, the Doctor is unintentionally roped into a caper with his missus, River Song. Unfortunately, she doesn't recognise him due to the fact that they meet out of order (and she's not met this version), with hilarious consequences.
The Doctor quotes Hamlet, or something close to it and does end up getting very hammy at points in this episode. All the Doctors have eaten scenery at one point or another, including Capaldi, who is a good enough actor that he can overact effectively - most notably the scene where he does the whole "bigger on the inside" speech. He does a good job here, having gotten the 'old grump act' down to a fine art, but he really needs a proper companion to fully ground him. He makes a rather Bond-esque quip at the demise of one character, which is definitely off and his comment at a crash site that there's no-one worth saving also seems very cold.