Jon Pertwee arrives in earth, staggers out of the Tardis and falls over. He has regenerated. Meanwhile, UNIT is tracking meteorites that mysteriously fly in formation. (Rather like those in Quatermass 2, actually.) Enter sceptical scientist Liz Shaw, the Brigadier, an amusing poacher chappie, some plastic blokes with guns literally in their hands, and the first colour telly version of DW is under way. It's classic stuff, for all its faults. The plot is a tad convoluted, the Autons look at a mite unconvincing at times, and the actual Nestene that controls them is very silly. But the general level of acting is high, the script is good, and the direction above average. Throw in Pertwee's dandy Doctor - by turns charming, irascible and impulsive - and you've got a winner.