"All right, let's move." he says, as he looks both ways over the mostly deserted cobble street and darts across into the shadows between two houses on the far side. He turns, beckons for Isma to follow, and then vanishes as he heads around the corner of the next building.
Saving some inane conversation: Assuming you follow, when you arrive there, you can see that the window on your side of the building (if west was the front. facing the road, you're on the south side now, approaching along the buildings on this street) is open. If you get to where Gelvin is crouched, he will beckon you to go first into the window while he covers you, and that he will follow close behind. Make any relevant checks you'd like to, and if you miss any (or any passive stuff is needed) needed in the time ahead, I can make them.
Also, if you don't want to put the time into this, as the zombie game is looking to shape into something quite cool and perhaps time intensive, I'm fine if you want to quit, mine may end up boring. We've had a rough start, but I like where it's going to go if we continue, too, I think, so your call.