The Doctor gets involved in a struggle of power between the citizens of Vulcan and rebels. However, one of the government's scientists has found a capsule in a swamp, which contains old, deactivated Daleks. After reviving them, they plot to overthrow both the Rebels and the Guards, and the serial ends in a climactic duel.
I must say, this has been one of my favourite serials so far. The Doctor is on top-form, the Daleks are great, and the characters of Bragen, Lesterson, and Henshall are all great to watch. Complementing them is a fast-paced plot which is more action orientated than previous stories have been, and this is a breath of fresh air.
Did I mention the Daleks are back? They're scary, and it's even more scary to see Daleks pretending to be under human control but actually plotting themselves. It's gripping stuff.
Overall, a great serial for the introduction of Patrick Troughton, and the story is insightful as to the direction Doctor Who is taking.