Prisoners is the sixth Jack the Ripper memory, dated 9 November 1888: Evie goes downriver to Deptford to free Jack's hostages from prison hulks and an old garrison, and to kill Chief Warder John Billingsworth, the hangman running the place.
Part 6 of 10 in Sequence 10: A Monster's Creed
The prison ships are old navy vessels once used to hold convicts. Climb aboard and talk to the caged hostages: none of them knows why they are there, and they tell you Jack has not visited for weeks.
Use the viewpoint to scout the garrison. Take keys from the head guard, then blast open the cell where prisoners are planning a breakout; they keep the guards busy while you slip into the warder's area.
Jam the gallows pulley so his assistant goes up to fix it, then work the pulley again so it hauls Billingsworth up by the leg, and finish him with the Hidden Blade.
Telephone Scotland Yard from a nearby building and ask for constables to be sent to the hulks, then hand the cell keys to the hostages on the way out. The officer on the line tells Evie the Ripper has struck again.
Before he dies, the warder taunts Evie that the whole operation was Jacob's idea and that her brother taught Jack. Evie refuses to believe it.
John Billingsworth once worked as a government hangman and was dismissed for an excessive taste for sadism. He keeps records of his hangings and tries to beat them, which is why the hostages dread his assistant asking how much they weigh.
Loose Ends
Loose Ends is the seventh Jack the Ripper memory: you play as Jack, returning to the Deptford garrison after Evie's raid to kill the witnesses and burn the evidence before the police can connect him to the Assassins.
Letters of Intent
Letters of Intent is the fifth Jack the Ripper memory, dated 3 November 1888: Evie gets a lead from Abberline, rescues newspaper owner Arthur Weaversbrook from Rooks near St Paul's, and then frees his kidnapped son from Jack's men at the docks.
The Mother of All Crimes
The Mother of All Crimes is the eighth Jack the Ripper memory, set on 9 November 1888: Evie examines the scene of Mary Jane Kelly's murder, then follows a message from Jack back to the earlier murder sites in Spitalfields and Mitre Square, searching for clues without killing anyone.
Autumn of Terror
Autumn of Terror is the second Jack the Ripper memory: Evie Frye arrives at Scotland Yard in October 1888, learns from Inspector Abberline that Jacob is missing, and rides with him to Whitechapel to investigate the first murder scene.