The TARDIS lands in the middle of what appears to be a first world war battlefield. As shells begin to fall, the Doctor, Zoe and Jamie seek shelter in a bomb crater. They are rescued by an ambulance driven by Lady Jennifer Buckingham (Jane Sherwin) who explains that they are in no-man's land. 

The ambulance is captured by German troops who are in turn overpowered by a group of British soldiers, led by Lieutenant Carstairs (David Savile). Once in the British trenches the time travellers are keen to return to the TARDIS but instead are taken before Major Barrington (Terence Baylor) to explain their presence at the front lines. Barrington informs his superior, General Smythe (Noel Coleman), about the strangers and he tells Barrington that they are enemy spies and orders them sent to the General's HQ in a nearby chateau. Smythe retires to his room where he uses a monitor device hidden behind a painting to order 5,000 more 'specimens' to be sent to the zone. 

After a rigged court martial, Smythe orders Jamie to be sent to the Highland regiment for a further court martial, Zoe to be sent to a civilian prison and the Doctor to be shot. 

During the night, Zoe manages to sneak into Smythe's empty bedroom looking for the keys to the cells. She also discovers the hidden monitor. She rescues the Doctor but they are unable to get away before Captain Ransome (Hubert Rees) arrives with the firing squad. 

The Doctor's execution is prevented by a sudden German attack. Zoe and the Doctor manage to escape and go in search of Jamie, who is being held in the military prison. The Doctor and Zoe pretend to be war office inspectors and get Jamie brought to them. Before they can escape, Ransome arrives and they are taken back to the chateau. Carstairs and Jennifer tell the Doctor and his friends that they felt that the court martial was unfair. Zoe tells them about the device in Smythe's quarters and they all sneak into the General's room. 

Jennifer and Carstairs cannot see the machine at first but the Doctor urges them to look harder and the monitor fades into view. Smythe is watching the events from the other end of the monitor's connection and rushes back to the zone in a TARDIS-like device called a SIDRAT. 

The fugitives flee the chateau in Jennifer's ambulance and head for the edge of Carstairs' map. Smythe orders artillery fire to destroy the ambulance, hypnotising Ransome with a special pair of glasses to arrange the attack. 

The ambulance drives through a heavy mist and when they emerge they find themselves under attack from a Roman legion. They reverse back into the first world war zone. 

The Doctor explains that the mist is a gateway joining different zones in time. He tells his friends that they must locate a map of all the zones to find those controlling the war games. They head back to the chateau to steal Smythe's map. Overpowering the guards, they blow open the General's safe and find a map divided up into triangular zones with a blank triangle in the centre. The Doctor deduces that the zones will be controlled from there and that they must make their way to it. 

The Doctor, Zoe, Jamie, Carstairs and Jennifer travel through the German lines and are captured. The Doctor tries to explain the truth but Major Von Weich (David Garfield) has, like Smythe, a monitor device in his room. 

In the central control area the War Chief (Edward Brayshaw) is told by Smythe about the Doctor and his friends. The War Chief orders their capture and interrogation in the control area. 

The Doctor and the others escape from the Germans and arrive in the American civil war zone. They are quickly ambushed and Carstairs is captured. 

The Doctor, Jamie, Zoe and Jennifer rest for the night in a barn. A SIDRAT suddenly appears and a large number of hypnotised union and confederate soldiers disembark. The Doctor enters the machine to investigate, but the sound of gunfire begins outside the barn and Zoe goes inside to warn the Doctor. The SIDRAT dematerialises leaving Jamie and Jennifer behind. 

The Doctor and Zoe find that the SIDRAT is a time/space machine like the TARDIS, filled with hypnotised soldiers from many different Earth wars. The Doctor plans to stow away until the ship returns to its base. 

Jennifer and Jamie are tied up by union troops but the confederate army overruns the barn and they are about to be set free until the confederate General - who is the same person who claimed to be Von Weich - announces that they are enemy spies. 

The War Chief expresses his anger over the growing rebel movements in the war zones. Over five per cent of the hypnotised soldiers break through their programming after time. He orders the Chief Scientist (Vernon Dobtcheff) to improve the processing machines. 

The SIDRAT arrives back at the landing zone in the control area. The Doctor and Zoe leave and don the slit-like glasses worn by the humanoid aliens in the control zone. Mistaken for students, they are taken off to a lecture about the processing machines. 

A union soldier sneaks into the barn and unties Jamie and Jennifer. They get away, but their rescuer is caught and taken before the General who tries to hypnotise him. The solder is immune and a member of the rebels. 

In the lecture, Carstairs is to be used as the subject of a new, more powerful processing machine. The Doctor tricks the scientist into showing him how to alter the machine to de-process the humans. At that moment the War Chief enters the room and recognises the Doctor. He and Zoe run off. 

Jamie and Jennifer meet up with the rebels who return to the barn and capture the General. They then wait for their leader Sergeant Thompson (Bill Hutchinson) to arrive. 

Zoe is captured and brought before the Security Chief (James Bree) for interrogation. Using a helmet-like device he probes her mind about the rebels and their leaders. Zoe sees pictures in her mind of all the important rebels in the different zones. 

The Doctor returns to the scientist still working on Carstairs. He tricks the man into de-programming Carstairs and they trap the scientist in his own machine. 

The confederate General manages to alert the War Chief. The Doctor and Carstairs rescue Zoe who tells them about the helmet device and that she has committed all the rebels names and faces to memory. The Doctor plans to return to the zones and organise all the factions into one large army. They head back to the landing bay. 

The War Chief and the Security Chief argue over how to handle the rebels in the barn. The Security Chief sends a group of guards in a SIDRAT but Jamie had suspected this and the rebels hide and kill the guards when they emerge. Jamie and Thompson take some men and go into the SIDRAT whilst Jennifer stays to tend to the injured rebels. 

The SIDRAT is detected on its return and armed guards are sent to meet it. Jamie, Thompson and his men are ambushed and captured. The Doctor, Zoe and Carstairs watch the events from hiding. 

The Security Chief accuses the War Chief of being in league with the Doctor. The War Chief admits that the Doctor is a Time Lord like himself but denies any collaboration. He threatens to tell the War Lord about the Security Chief's continued incompetence at failing to capture the Doctor and his friends. 

The Doctor, Zoe and Carstairs hide in a uniform store next to the processing room. The captured Jamie is taken to see the Security Chief while Carstairs knocks out the guard and allows the other rebels to escape. 

The Doctor rescues Jamie and, disguised in First World War uniforms, they head for the landing bay where Zoe and the rebels leave in a SIDRAT. The Doctor, Jamie and Carstairs double-back to steal the processing machine. They succeed and manage to get into a SIDRAT just as the War Chief and his guards arrive. The War Chief adjusts the dimensional controls and the interior of the SIDRAT begins to shrink. The Doctor is forced to leave the ship but instead of surrendering, he uses a gas bomb to divert attention while he re-sets and locks the remote controls to the SIDRAT. 

The War Lord (Philip Madoc) arrives from the aliens' home planet and the War Chief tells him that everything is under control. 

The rebels head for the First World War zone and attack Smythe's chateau. They seize the building and kill Smythe. The Doctor uses the devices in the General's room to set up a barrier around the chateau to protect it from attack by human soldiers. 

The War Lord orders a SIDRAT to be sent to the chateau where the guards seize the processing machine and the Doctor before escaping. The rebels start to contact all the other rebel groups in order to pool their resources. The Mexican leader Arture Villar (Michael Napier-Brown) is suspicious but eventually agrees to join the plan. 

The rebels systematically attack the monitor devices throughout the zones forcing the Security Chief to send guards into the zones leaving the control centre poorly guarded. 

The War Chief takes the Doctor away to interrogate him personally. He asks the Doctor to join him. He plans to help the War Lord's people in their plan to use human soldiers in their conquest of the galaxy, but the War Chief intends to seize control after the fighting is over. 

The Security Chief is keen to use a neutron bomb to destroy the rebels, but the War Lord agrees to the War Chief's plan. The Doctor will lure his friends into a trap. The Doctor contacts the rebels and says he is sending a SIDRAT to fetch them. Once they land, the rebels are captured and taken away for processing. 

The Doctor tells the War Lord that he can adjust the processing machines to make them more efficient. The War Lord agrees and orders the Doctor to begin by processing his ex-friends. 

The Doctor processes Jamie first under the watchful eye of the War Chief, but the Doctor has adjusted the machine to have no effect. The War Chief is convinced by Jamie's acting and leaves the Doctor to process the rest of the rebels. The rebels overpower the guards and the Doctor explains that he pretended to help the War Chief to prevent them all being killed by a neutron bomb. 

The Security Chief has secretly recorded the War Chief's conversation with the Doctor and orders the War Chief to be locked up. He is marched off by two guards who are attacked by the rebels. The War Chief agrees to help the Doctor stop the fighting in the zones. The rebels attack the control room and the War Chief kills the Security Chief. 

The Doctor wishes to use the SIDRATs to send all the soldiers home to Earth but the War Chief reveals that only two machines have any power left in them. The Doctor is forced to contact his own people for help. He mentally assembles a message box which contains all the information the Time Lords need. The War Chief is frantic and runs off. He reaches the landing bay but the War Lord is waiting and his guards kill the Time Lord. The rebels arrive and capture the War Lord. 

The Doctor sends the message box to the Time Lords and tells the rebels and his friends that he must leave before the Time Lords arrive. Jamie and Zoe refuse to stay behind and the Doctor agrees to take them with him back to the TARDIS. 

The Time Lords fail to prevent the Doctor's escape and he tries to pilot the ship away. He explains to Jamie and Zoe that he was bored living in an advanced society of great power who had strict laws of non-interference in the affairs of others. He had to steal the TARDIS and escape in order to see the wonders of the universe and fight evil. 

The Time Lords force the TARDIS back to the Doctor's home planet. 

They leave the TARDIS, and a Time Lord (Clyde Pollit) orders them to follow him. The trial of the War Lord is underway and the Time Lords (Bernard Horsfall, Trevor Martin) call the Doctor as a witness. Before the Time Lords can pass sentence, a SIDRAT lands and a group of alien guards storm in and rescue their leader. They take the Doctor, Jamie and Zoe hostage and order him to use the TARDIS to help them escape. The Doctor causes a blinding flash and while the aliens are blinded he, Jamie and Zoe run out of the TARDIS. 

The Time Lords throw a force-field around the War Lord and his guards. Their sentence is that their home planet will also be enclosed by a force field and cut off from the universe forever, whilst the War Lord and his accomplices are dematerialised out of existence. 

The Doctor's own trial now begins. He argues that although he is guilty of breaking the law of non-interference, the Time Lords themselves are also guilty of failing to use their powers to help others. 

Whilst the three Time Lords deliberate the Doctor's plea, Jamie and Zoe are returned to their rightful times. They will only remember their first adventure with the Doctor. 

The Time Lords pass sentence on the Doctor. They accept his plea that evil needs fighting and have decided to send the Doctor to Earth in the twentieth-century with the secret of the TARDIS taken from him. The Doctor argues that he is known on Earth and the Time Lords explain that he will change his appearance again. 

The Doctor refuses each suggestion for his new appearance and eventually the Time Lords choose for him. He disappears from the courtroom and reappears on a monitor where his body spins away into blackness as he continues to protest.

_{Synopsis from Doctor Who: The Second Doctor Handbook by David J. Howe, Mark Stammers and Stephen James Walker, reprinted with permission; further reproduction is not permitted. Available from Telos}