Holmes and Watson examine one of the bodies from the botched arson attempt earlier, and determine that he had spent time at a meat factory across town. They find a lab at the factory which is very similar to the midget's from before, and then see hundreds of pigs hanging up on meat hooks. Blackwood scares them and introduces a new problem - Irene is bound to a hook, and the machine starts up about to slice and dice her.
The detectives rescue her and then chase after Blackwood, but he has rigged explosives along the docks which injure Watson and aid his escape.
Holmes is now wanted by the police for questioning, but manages to get to his apartment and delves into some black magic to help him with the case. Holmes thinks he knows where the next target will be as the police show up. Watson and Irene escape as Holmes is arrested by Lestrade.
Holmes is taken to the Houses of Parliament and to Blackwood's right hand man, but he blocks the chimney flue, so that the room fills with smoke and he jumps out the window diving into the Thames to be picked up by Watson in the boat from before.
Knowing a little more about Blackwood's plan now, the three heroes get to the sewers and find a machine ready to dispense a chemical into the Houses of Parliament. Some goons show up for a fight, including the French giant.
Blackwood announces his plans for change to the House of Lords, while the Men of the Order bar the doors. He is about to trigger the chemical system by a remote control.
Irene grabs the chemicals and races off with them, chased by Holmes. Blackwood has realised his device isn't working, and quickly in the sewers himself also gives chase.
They somehow all emerge on top of the Tower Bridge, which makes no sense at all, and Blackwood throws Irene off the scaffolding. Holmes and Blackwood fight a little, and Holmes details how he solved the crime, including: the grave stone was glued together and could be easily broken, the guard at the prison was paid to foam at the mouth, the old man from The Order who stood up to Blackwood was ignited by a spark from his gun (which just shot a blank) as he was covered in gas from sprinklers outside the building, there was a chemical in the bath tub which killed Blackwood's father, and the men from The Order all drank a potion to act as an antedote against the toxin.
Blackwood is being pulled by a heavy metal anchor to his death but Holmes helps him up so he can go to jail where he belongs, and then they fight some more as Blackwood pulls a pistol - but this time falls again and the rope falls around his neck leaving him hanging from the bridge for everyone to see. Holmes then finds Irene who is still alive, but says his goodbyes as she is too much woman for him or something like that.
Later, Watson and his fiancee visit Holmes - who is hanging from a beam and presumed dead, but is really trying to figure out how Blackwood mastered the other tricks. It seems he had a hook on his belt which helped displace his weight, and Watson shouldn't feel bad as he used a chemical to make him appear dead - which he has tried out on the dog.
He then realises that Moriarty, the man Irene was working for, was not after the chemicals but secretly returned to the machine to pick up the radio device, and is a powerful mastermind criminal he will no doubt meet again very soon.