The Doctor and his friends find themselves in Bradgate after a harrowing experience in the TARDIS in which Barbara was possessed by a Vrij and tried to strangle Ian. The Vrij escaped and brought the TARDIS to the 16th century.
Barbara is nearly attacked by a wolf that is possessed by the Vrij, with Ian unable to help, but at the last minute the wolf is killed by a young girl. The man who accompanies her, the Duke of Northumberland, points out her kill to the other men with them, then threatens Ian and Barbara with death if they cannot account for their presence here. They are too shaken with fear to answer, but the Doctor arrives just in time. He examines the wolf, noting that the Vrij has escaped. When the duke threatens him, the girl pretends the Doctor is the tutor she has been expecting. The duke, her uncle, escorts the trio back to the girl's home.
As the Doctor teaches the girl, he realises she is Jane Grey, who is destined to become queen soon. He asks her why she helped him, and she states that she will help him and his friends leave, on one condition — they take her with them. Her parents want her to marry against her will.
As the Doctor works on a device to capture the Vrij, Barbara approaches him with concern about Jane, but as before, he reminds her that they cannot change history.
The wedding takes place, with the Doctor and his friends in attendance. The Doctor's tracer detects the presence of the Vrij in the church, and Barbara sees a shadow fall over Jane. They believe that the Vrij has now possessed Jane.
Prior to Jane's coronation, strange things begin to happen, such as ghosts and stillborn children. The Doctor believes this is a result of the Vrij stirring itself.
The Doctor and his friends attend the coronation. Later, the Doctor tries to get close to Jane, and he overhears her conversation with her uncle. Her uncle wants her to make her husband, his son Guildford, king, which she cannot do by law. The Doctor believes the Vrij is possessing the duke and confronts it, and it attacks him. Barbara finds the Doctor seemingly dead, but the duke has left. Barbara attempts first aid, but the Doctor wakes on his own and scolds her, saying he was in a restorative coma. Jane is frightened but relieved that the Doctor is alive.
The Vrij has altered history. The duke has been able to raise an army of thousands against Mary's attempts to take the throne from Jane. He and his friends hide in the duke's room with the finished device, which will suck the Vrij into a dimensional trap. When the duke arrives, the Doctor taunts the Vrij until it attacks him and is trapped.
The Doctor and his friends prepare to leave the 16th century. Meanwhile, Jane steps down from the throne and is imprisoned. A year later, she is executed.
- First Doctor
- Barbara Wright
- Ian Chesterton
- Jane Grey
- Katherine Grey
- Anne Grey
- Duke of Northumberland
- Guildford Dudley
- Jane reads Plato's Phaedo in the original Greek.
- Some people think Henry VIII's ghost is walking the streets.
- During their year of imprisonment, Jane read the Bible to Guildford.
- In 1985, Barbara will write a GCSE textbook called Journeys Through History: A Sourcebook for GCSE for the Associated Exam Board with Ian Martin, in which Lady Jane Grey's brief reign is covered.
- The stories in Decalog 2 have a common theme of homes owned or acquired by the Doctor. The home in this story is the house in Islington given to the Doctor by the Duke.
- The Doctor uses a device when somewhat resembles the sonic screwdrivers used by his later incarnations, although this device is explicitly a tracking device used to track the Vrij. It is described as a "thin cylindrical rod", with a complex wire aerial extending at the flick of a switch and a tiny control panel. He eventually breaks the device when it starts incessantly beeping during Jane Grey's wedding ceremony.
- Ian and Barbara recall their first meeting with the Doctor in Totter's Lane. (TV: An Unearthly Child)
- Lady Jane Grey was visited by another time traveller, Rani Chandra during events which overlap with those of this story. (TV: Lost in Time)
- Barbara thinks Jane reminds the Doctor of Susan. (TV: The Dalek Invasion of Earth)