- "It's not chance, Mr Holmes, it's chess. It's a game of chess."
- ―Jeff on his game [src]
Jeff Hope was a serial killer operating before and during the first episode, "A Study in Pink". Not much is known about the taxi driver, except that he has two children, is estranged from their mother, and has a life-threatening aneurysm that could kill him any time. Jim Moriarty sponsored Jeff's killing spree, with money going to his children for every life he took. Jeff kills four people before he is stopped by a bullet from John Watson.
Hope kills his victims by kidnapping people that get into his cab and taking them to an empty building. There he makes them play his game. His game is to offer his victims the choice of which pill they want to take out of two identical pills. One pill, referred to as the "good pill," will not kill them, however the "bad pill" will.
Hope gives his victims the choice of which pill to take. In turn, he takes the pill they did not choose. If the victim refuses to take either pill, he opts for them to take a bullet from his gun, which they never choose. In actuality, this gun is merely a lighter and therefore a ruse to coax them into ingesting the pill. Only Hope himself is aware of which pill is the good pill and which is the bad pill.
Hope's method of killing confuses the police as they see the deaths as suicides and do not see how suicides can be linked in any way. All they know is that four people committed suicide using the same poison with each victim being found in a location in which they had no business being. The police bring Sherlock in to see the Jennifer Wilson crime scene, where Sherlock deduces that the deaths are murder.
Aware of Holmes's involvement in the investigation, Hope makes contact with Holmes and takes him to an empty university to explain the rules of the game. Although Holmes deduces that the gun is a fake, the challenge to his intellect to work out which pill is the 'good' pill is too great, and he remains for a time contemplating the situation until Doctor Watson tracks him down and shoots Hope, taking the choice out of Holmes' hands.
- "I'm not going to kill you, Mr Holmes. I'm gonna talk to you, and then you're gonna kill yourself."
- ―Hope explaining the method behind his madness.
Jeff Hope has a rather analytical personality, as through his various attempts to ensnare Sherlock Holmes. He is treated as a genius on the same level as Holmes, in which he uses his taxi driver alias to full benefit in escaping unnoticed from Holmes' first meeting with him. Hope is initially unmoved by Holmes' original threats, explaining that he believes strongly in chance. However once he gets shot by Dr John Watson, he responds to the pain by telling Holmes the name of his enemy, Moriarty.
Jeff Hope's relationship with Sherlock Holmes is that of a mutual connection with one another, in which both recognise the level of their intellect is at the same pinnacle. Through this, Sherlock attempts to see through Hope's ingenious plan by placing himself in a compromising position.
It is uncertain whether Jeff Hope and Jim Moriarty ever directly met. However, they did establish a deal in which Moriarty allocates more money for Jeff's children every time Jeff "kills" a person.
Jeff Hope has a strained relationship with his former wife who retained custody of his children after their divorce. Although he kept a family picture of his wife and children in his taxi, he purposefully cut his wife out of the picture, symbolically representing his hatred of her.
During Moriarty's court case, one of the jurors is shown having her children threatened by Moriarty via television. This juror looks conspicuously like Hope's estranged wife, and the children shown have a remarkable similarity to the children in the photograph.
After his separation with his wife, Jeff Hope still maintained a strong love for his two children, even resorting to leave a picture of them attached on his dashboard in his taxi. Hope's love for his children went so far that he was willing to kill innocent people in order to ensure they had a proper future.
- This character is an update of Jefferson Hope, the primary antagonist from the original Sherlock Holmes novel, A Study in Scarlet.
- Jeff is cab driver #71126.