I wasn't in a fit state to pay much attention at the time, but I was later able to piece together what happened next from the reports of others.
The force of Goblin cops pointing guns that had surrounded Garrick had evidently taken him unawares. For once, he was nonplussed, uncertain what course to take. Fortunately - for him - the decision was taken for him.
When a copper from the Lower Realms tells you this, he really means it. All Goblins know that even a minor movement can be the trigger for a glamour, and so the police are trained to shoot first and pick up the pieces afterwards. The old Professor also knew this, unsurprisingly, and kept his hands motionless and well away from his body.
At a nod from Luncardy, one of her crew deployed a disabling glamour - again, a magic rarely used and legal only when deployed by sanctioned members of the police force. Threads of silver and ribbons of lilac appeared from nowhere, folding themselves around Garrick's body like some elaborate giftwrap, a perp in translucent silver foil. These glamours are required to suppress all magic and slow bodily movements, and few are able to counter their effects. Garrick was not one of them.
The Professor was formally arrested; extremely formally: encased in the festive wrapping of the disablement magic, he was addressed using the archaic words long custom has required. Some humans might think them similar to Miranda Rights although in truth they are rather longer and much more complicated. After that, he was taken away - quite literally carried bodily from the area in the cocoon of magic by four burly coppers, deposited in the back of a human-scale transport and rushed to the nearest entrance to the Lower Realms.
At first, it was expected that Professor Garrick would stand trial in the usual way, Goblins being, generally speaking, fanatical about the rule of law, even those who spend most of their time circumventing them. But it was not to be. By instruction from the Senate - this is a conventional form of words that indicates that somebody in a position of real power has taken an interest in the matter - Garrick was transferred to a secure institution: a place reputed to be genuinely impossible to either escape from - using magical as well as physical methods - or to bribe your way out. Garrick might have had friends in high places, sympathisers with his objective to returning to the surface world. If he had, none of them put their heads over the parapet to support him now.
In another place not far away, a quiet copper from Luncardy's force gently disengaged me from Trinity's silent corpse and led me away. It was a long time before I was able to piece my life back together again.