(I wrote this up once but forgot to save it. That was a month ago! Grrr)
The party was looking for trouble and found it when a section of outer wall collapsed and trolls started pouring in. The city guard rushed to stop more trolls from entering but a half dozen were already in and it was up to the heroes to stop them!
The heroes prevailed but were beaten and bloody. They wanted to help the guard but were too hurt themselves, so they returned to their barracks for some healing oils, warm beer, and a nap.