When last we left off, I mentioned that the Second Doctor had been forced to regenerate and was exiled on Earth for his interference in the affairs of humans and aliens during his travels—so sayeth the almighty Time Lords of Gallifrey. The Doctor's new form, his third, was played by Jon Pertwee (pictured left).
The Third Doctor made the best of his exile and formed a working relationship with UNIT, the United Nations Intelligence Taskforce, under the command of Brigadier Lethbridge-Stewart (pictured right). How this era fits in with the Torchwood Institute's edict of keeping the Doctor out of the British Empire (see "Tooth and Claw") has yet to be explained. In any case, the Doctor faced two seasons' worth of aliens before opening Season Nine with Day of the Daleks.
In Day of the Daleks, rebels from the future (the 22nd century, evidently from a different era than the folks we saw in The Dalek Invasion of Earth) travel to the 20th century to stop the sabotage of a peace conference. Sabotage that would lead to a hundred years of war and a defenseless Earth ripe for picking by... (you guessed it) the Daleks! The Doctor travels to the future to face off against his old foes but is captured along with his companion Josephine 'Jo' Grant (in the middle of picture on the left). After a brief interrogation, the rebels rescue the Daleks' prisoners and the Doctor returns to the 20th century. A bomb constructed by the rebels is used to destroy the house of the peace conference as well as the following Daleks and their minions (after Brigadier Lethbridge-Stewart evacuated it of dignitaries). The sabotage believed by the future rebels to lead to a century of war was actually the explosion of the house. History is saved once again.
The following year, the Daleks returned to give our hero grief in Planet of the Daleks. The Doctor and Jo arrive on the planet Spiridon and encounter a group of Thals from the planet Skaro. You might remember the Thals as the people who fought a war with the Dals, the precursors to the Daleks. Spiridon is ruled by an army of 10,000 Daleks, whose plan is to unleash a plant-killing bacteria. The Doctor stops this nefarious plan using a bomb to unleash "molten ice," freezing the Dalek army in their tracks and thoroughly pissing off the Dalek Supreme (an earlier version pictured right).
The Third Doctor's final encounter with the Daleks came in the middle of Season Eleven with the story arc Death to the Daleks. A TARDIS malfunction results in an unexpected trip to the planet Exxilon where the Doctor and Sarah Jane Smith (Jo left to get married at the end of Season Ten) encounter some Space Marines and eventually... the Daleks. The Daleks, like the Space Marines, have come to the planet to mine a valuable ore that can cure a plague currently ravaging human and Dalek planets alike. Both sides reluctantly work together (neither has power e.g., no weapons) until the source of the power drain is found and destroyed. However, the no good Daleks attempt to screw our heroes royally by firing a plague missile at the planet. Their double-cross backfires when one of the Space Marines detonates a bomb aboard their ship after stowing away.
The Third Doctor didn't meet as dignified an end as his predecessors. Radiation from a race of giant spiders eventually killed him when he returned to UNIT headquarters. With assistance from a fellow Time Lord, our hero regenerated into the Fourth Doctor, a role made famous the world over by master thespian Tom Baker and his giant scarf.