Tobias Gregson

Tobias Gregson helped Mael Stronghart frame Genshin Asogi for being the Professor, to which he opposed at first, until Stronghart convinced him that this would be necessary to prevent Genshin from claiming any more victims, as Gregson mistakenly believed Genshin was the Professor. He hired a group of mercenaries to attack Genshin, stealing his trademark ring. Then, with Stronghart's help, Gregson would argue for Klint van Zieks' autopsy report, which would not normally be done to a noble in the House of Lords.

After that, he helped Stronghart spread the "Reaper of the Bailey" conspiracy. During this time, Gregson would investigate guilty defendants prosecuted under Klint's younger brother Barok who twisted their own trials to escape justice, and come up with the best ways for Britain's notorious assassin, Asa Shinn, to eliminate them.

Gregson also took interest in Daley Vigil, a former employee from Barclay Prison who was terminated following complications arising from the Professor case, and was masquerading as a street vendor named "Hugh Boone". To that end, Gregson paid Vigil to use his ID and make a public scene wherever he was directed, claiming the detective was there to investigate, in order to mask his movements around London. During that time, Gregson also grew close to Iris Wilson for helping further bolster his public reputation through her stories, to the point that he also became compliant to her own demands.

Eventually, Stronghart decided that Gregson knew too much about Klint's autopsy and his own past, so to eliminate Gregson, he had Genshin's son, Kazuma, kill him. Since by that point a treaty had been made between Japan and England, Stronghart knew if Kazuma was fully exposed of killing Gregson, England would have difficulty arresting the young Japanese man. Unfortunately, Stronghart's plan went wrong as Kazuma was knocked out and presumably killed by Nikolina Pavlova, sparing Gregson for some time.

While Gregson sent Vigil out to be a decoy with the "Red-Headed League", a small-time scam of Fabien de Rousseau and Peppino de Rossi, he was given a "Reaper” mission for October 31st aboard the SS Grouse as it headed for France. The target was Seishiro Jigoku, who was put on trial ten years ago when he made insulting remarks while trying to save Genshin Asogi.

Since Asa Shinn was killed, the assassin that would go with him was Kazuma Asogi. Before he left his secret room to go there, he spoke fondly of Lestrade, and left her his "detective spirit".

While in Seishiro Jigoku's cabin on board the Grouse, Gregson learns that Kazuma is Genshin's son. He tells him that he believes that his father was the Professor even now but didn't have enough evidence to prove it back then. He said he just worked as the mission instructed for the British Empire. But Gregson refused to say exactly what he did, even if it meant his death. This caused Kazuma to furiously draw his sword and swing, not hurting the detective but chipping Karuma on Gregson's trunk.

Then Kazuma decided to leave, disembarking in Dunkirk, France to stay the night, so Gregson decided to kill Jigoku all by himself. But Jigoku didn't know Kazuma Asogi was alive and had already decided to kill Gregson on his own to complete the assassination exchange program. The "Reaper" mission assigned to Gregson was a fake asked by Jigoku himself. When Jigoku returned to his room, he found Gregson there.

He choked Gregson, knocking him unconscious before the other could shoot him. As first-class cabins are surrounded by guards, Jigoku decided to wait until the emergency drill later that evening to strangle him to death. Unfortunately, just as that time arrived, Gregson woke up and started attacking Jigoku in a frenzy. In a moment of panic, Jigoku used the gun the English government had given him in the exchange program sixteen years ago and shot Tobias Gregson, killing him instantly.