Doctor Who Season 4 Episode 4 The Sontaran Stratagem

Doctor Who The Sontaran Stratagem 4/13

A journalist, Jo Nakashima, attempts to interview a boy genius named Luke Rattigan about his invention, the carbon-cleaning car filter/GPS navigation system known as ATMOS. She believes it is dangerous, but has no proof, and so he throws her out. As she attempts to report her findings to UNIT, Rattigan informs his unnamed superiors about her, recommending that she be terminated. They agree, and moments later her car takes control of itself and drives her into the river.

Martha Jones calls the Doctor for assistance. She is now working for UNIT, and, having just raided the main ATMOS factory, they need his help in determining if the ATMOS system is alien in origin. Though it is much more advanced than human technology should be, the Doctor notes that it is entirely human-made. He also notes that there are 800 million cars in the world, which would equal 800 million weapons if ATMOS could control every one. Donna points out that while the system may be man-made, the factory workers do not seem quite human, as not a single one has ever taken a sick day.

While they prepare to examine the workers, two UNIT soldiers stumble upon a cloning facility in the basement. There they are confronted by a Sontaran, who identifies himself as General Staal of the 10th Sontaran Battlefleet, or 'Staal the Undefeated', who disables them and has them hypnotically converted into loyal servants. They in turn kidnap Martha, who is cloned by the Sontarans and kept prisoner so the clone can access her memories.

The Doctor decides to check out Rattigan, while Donna heads home to check on her family under Martha's advice. At Rattigan's school, the Doctor confronts him about the fact that he did not invent the ATMOS system, as though it is human-made, the technology is far too advanced. He also points out the very large teleportation device sitting in the middle of his room.

The Doctor quickly uses it to teleport to the Sontaran's battleship, getting one (General Staal) to follow him back before disabling the teleporter. After giving a quick run-down of Sontaran history, revealing that the Sontarans developed the ATMOS technology, he uses a squash-ball to injure the probic vent on the back of the Sontaran's neck, which is their only weak point.

On the Sontaran battleship, Rattigan's off-hand comments about the Doctor reveal his identity to the Sontarans, and General Staal, still irked about his race not being allowed to fight in the Time War, relishes the prospect of slaying the Doctor in battle. The Sontarans attempt to make the Doctor's ATMOS-equipped jeep deadlock itself and drive into the river, but the Doctor, realising that the ATMOS device is programmed to do the reverse of everything he says, instructs it to drive into the river; the resulting logical paradox overloads the machine and unlocks the doors, allowing the Doctor to leave the car before the device self-destructs.

Though only half the cars worldwide use ATMOS, the Sontarans realize that their plans need to be accelerated. They activate converters in each ATMOS system, pumping out poisonous gas from 400 million cars worldwide. They deadlock each one to keep the Doctor from interfering.

The Doctor tries to warn UNIT, but since it is the Martha clone he calls, they remain uninformed.

Meanwhile, Donna's grandfather is trapped in his car whilst attempting to get it off the road, the Doctor having realised what the ATMOS devices are for, and despite their best efforts the Doctor and Donna cannot free him as gas from the devices sprays into the car.

As the episode ends, the Sontarans prepare their soldiers for invasion and begin chanting battlecries, mentally readying themselves for battle, while the Doctor watches as hundreds of cars release the poison, powerless to stop them.