The Third Doctor (Jon Pertwee) and Sarah Jane Smith (Elisabeth Sladen) are planning a beach holiday but the TARDIS crash lands on the planet Exxilon. All the electrical power systems have been drained, so the Doctor lights an oil lamp (he has one in a cabinet) and they head out. The planet is a bleak wasteland populated by mysterious humanoids who attack and/or kidnap any aliens. The Doctor and Sarah Jane run into some humans who've come to the planet for a special element that will cure a disease infecting millions of people from the outer rim planets. Their ship is also powered down but they were able to send a distress signal before losing all power. They hear a ship coming and they hope it is the rescue ship. When the new ship lands, out come the Daleks! The Daleks have also lost power and they are forced to ally with the humans to solve their problems. Naturally, the Daleks make bad allies, but are they worse than the Exxilons?
The episode has an intriguing premise that plays out slowly but creatively. The uneasy alliance with the Daleks creates some nice tension (obviously the Daleks will turn on them the first chance they get, but how soon?) and the locals have an interesting culture. As is common on the old Doctor Who, the visual effects aren't always the best but the sound design is excellent. It's an enjoyable story and worth watching.