Theodore Maxtible is the secondary antagonist of the Doctor Who story "The Evil of the Daleks".
He was portrayed by the late Marius Goring.
Theodore Maxtible was a wealthy amateur scientist in Victorian England. One of his ambitions was to conquer the secret of time travel. He worked with fellow scientist Edward Waterfield, who lived in Maxtible's house along with his daughter Victoria. Maxtible also had a daughter, Ruth, but showed little interest in her and banned her from his laboratory. (The fate of her mother was not revealed.)
When Maxtible and Waterfield experimented using mirrors and static electricity, they opened a way through time for the Daleks to enter the house. The Daleks played on Maxtible's greed, offering him the secret of turning common metals into gold in return for him helping them. He hypnotised Victoria so the Daleks could take her hostage in order to gain Waterfield's co-operation. Maxtible pretended that was also his reason for helping them.
After Waterfield had retrieved the Doctor and Jamie from the 20th century, Maxtible joined him in explaining the situation to the Doctor. The Daleks intended to record human characteristics by observing Jamie during an attempt to rescue Victoria: These would then be programmed into three dormant Daleks. As part of the test, Maxtible manipulated Kemel, a Turkish strongman in his employ, into attacking Jamie, claiming he was an evil cut-throat.
When the Daleks killed Toby, a criminal who had tried to burgle the house, Maxtible was happy to hide the body but disconcerted when Waterfield revealed he intended to go to the police once Victoria was safe. Maxtible prepared to kill him but was stopped by Arthur Terrall, Ruth's fiance, who was also under the control of the Daleks.
Maxtible pestered the Daleks to give him the secret they promised but was met with threats and refusals at every turn. He was horrified to discover the Daleks had planted a bomb to destroy his house and, in terror, fled through their time machine to Skaro, ignoring instructions to bring the Doctor. He was imprisoned with Victoria and Kemel, and helped the Daleks lure the Doctor, Jamie and Waterfield into a trap by causing Victoria to cry out.
By now, everyone was aware of Maxtible's true nature. The Daleks set up a machine that apparently turned iron into gold, but as he approached it, he stepped through an archway that turned him mentally into a Dalek: The tests had shown the Daleks their own characteristics which they now intended to implant into all humans. Maxtible hypnotised the Doctor into also stepping through the arch but his non-human physiognomy protected him and he was able to switch capsules on the arch so, when the Daleks passed through it, they were given the human factor.
As war broke out between the Daleks still loyal to the Dalek Emperor and those with the human factor, Maxtible attacked an escaping Kemel, forcing him into a chasm to his death. He was then recalled into the city and staggered off into the carnage of the Dalek civil war, presumably perishing in the conflict and the resulting destruction of the city.