The Empty Hearse

Two years after his apparent death, Sherlock Holmes walks back into Dr John Watson's life. He doesn't do it gently. He does it in the middle of a terrorist threat, with London in danger and Mycroft calling his brother back to investigate an underground organisation. The reunion and the case arrive together, and neither gives the other room to breathe. The two-year question hangs over everything, and the episode knows it.

The episode has a fine line to walk. It has to deal with the two-year absence without drowning in it, and it has to give John his due: the man was told his best friend was dead, and he has rebuilt a life around that loss. Mary Morstan is in that life now, and she watches Holmes's return with a wariness that says more than the dialogue. For John, the hardest part isn't the surprise. It's that Holmes treats the whole thing as a detail, a puzzle solved and a point proved, while John is still carrying the grief. The episode is at its best when it lets that imbalance sit in the room.

Mark Gatiss, Steven Moffat and Arthur Conan Doyle wrote it, Jeremy Lovering directed. Benedict Cumberbatch and Martin Freeman are back at the centre, with Una Stubbs's Mrs Hudson, Rupert Graves's DI Lestrade, Mark Gatiss's Mycroft, Andrew Scott's Moriarty, Louise Brealey's Molly, Amanda Abbington's Mary, Jonathan Aris's Anderson and David Fynn's Howard Shilcott filling the edges.

The show knows its audience spent two years arguing about how he did it, and it refuses to take the reunion entirely seriously, which is the right call. The case, a shadowy underground organisation and the threat it poses to London, never quite matches the reunion, but it keeps the hour moving. But the episode earns its place by trusting the reunion over the plot, which is exactly right for a story called The Empty Hearse.