The Doctor, Leela and K9 are visiting Mars, sailing down one of the canals in the Doctor's houseboat, the Dejah Thoris. Mars has been terraformed by the Ares Corporation, the president of which is the Last Martian, the sole survivor of Mars' oldest indigenous species. The Last Martian is a cephalopod who was found at a dig site having been frozen for a billion years.
The Doctor and K9 attempt to find out the source of the red bloom at the Administry of Environmental Affairs, but they are captured. Leela, told to stay with the boat, instead follows the Doctor but gets lost. She finds her way into the mall and enters a diner called the Mars Bar. As she struggles with understanding the menu, a woman who introduces herself as Dr Ginger Corvette helps her order. Ginger, as an anthropologist, is interested in Leela's tribal behaviour. As they eat, alarms blare and the Doctor and K9 burst in. Suddenly an explosion rocks the diner; in the confusion, Ginger leads the Doctor and his friends away and back to the boat.
On the boat, they watch the news reports of the explosion. It is being blamed on Crimson Dawn, who the news claims is supported by the group Redpeace, which wants to give Mars back to the Ice Warriors. The news report also links the Doctor with the terrorists. The Doctor, hearing Ginger's report of the finding of the Last Martian in the city of Cydonia, decides to head to the city.
Ares meets with the Last Martian, who is paranoid about his safety. Ares decides to hold a stockholder meeting on the Last Martian's boat, telling him that he will be safe but secretly planning to kill the Last Martian.
As the Doctor's group examine the dig site at Cydonia, they are set upon by armed men — the members of Redpeace. The Doctor convinces them that they are on the same side and that he believes Crimson Dawn is not a terrorist group but rather a band of mercenaries hired by Ares to discredit Redpeace. The Doctor plans to access the Ares Corporation's records and meet with the Last Martian. He decides to attend the stockholder meeting.
The Doctor gets the information he needs and confronts the Last Martian. Ares, having been told of intruders, appears and trains a weapon on the Doctor. The Doctor accuses Ares of having created the Last Martian, and Ares confirms it. The Doctor goads the Last Martian into attacking Ares. The boat sinks in the shallow water, with the Last Martian escaping. The Doctor makes his way back to his boat.
The Doctor's group, Ginger and the members of Redpeace are on the boat when it is attacked by Ares in a jet-boat. Hilâl and other members of Redpeace are killed, and when the Last Martian attacks the boat, K9 electrifies the hull and Leela hits the Last Martian with a harpoon. Not sure if the Last Martian is alive, they don't turn on the boat engines.
As the survivors are comparing their wounds, Ginger tells the story of her life. The Doctor then accuses her of selling out to Ares, so she pulls out a particle bomb. The Doctor informs her that he has suspected her for a while, and that K9 has kept her under surveillance. Her bomb has been disarmed.
The Last Martian reappears, demolishing the boat and killing Ginger. Leela swims under water and kills the Last Martian with a janis thorn, though the cephalopod was also being killed by the red bloom.
An adjudicator is on the way to Mars, and the Doctor reveals that one of Mars's moons, Phobos, is actually a generational starship with a million Ice Warriors inside. When they are later awoken, the event is celebrated as Resurrection Day.
- Fourth Doctor
- K9 Mark I
- Dr Ginger Corvette
- Arif Hilâl
- Paul Ares
- Shunro Oshikawa
- Dr Sam Morgan
- The Doctor's canal boat is called the Dejah Thoris.
- The Doctor mentions Daleks and the Krynoid.
- Leela compares a waiter to a high priest of Xoanon.
- Eau d'Aggedor is a men's perfume from Peladon.
- The Last Martian references War of the Worlds by H. G. Wells.
- The stories in Decalog 2 have a common theme of homes owned or acquired by the Doctor. The home in this story is the Doctor's houseboat.
- The Doctor says he has a Villa overlooking the Lake of Mutations on Skaro.
- The Orion VI is a doomed science vessel.
- The Doctor tells Corvette that he has never seen the Martian Pyramid "from the outside". (TV: Pyramids of Mars)