The seal on the elevator doors is too tight for his swarm form to squeeze through. There is a very tiny gap at the top of the doors, however, that is just wide enough to allow one spider through at a time. The swarm seeps through, like a cloud of greasy smoke filmed in reverse.
Laurence scales the interior of the elevator shaft the three remaining floors and finds the same narrow gap at the top of the elevator's doors. One spide pokes through and peers around the lobby. There are two doors, one in either direction from the elevators. The door on the left is unmarked. The door to the right has the logo of the diamond exchange, and the door is cracked open. A man garbed in black fatigues, complete with a black cap and dark sunglasses, is watching the lobby. He's got a peculiar gun in his hands, about the size of a sub-machine gun, but of a design unlike anything he's seen before.
The man does not appear to notice Laurence's one spider peeking in through the gap. Laurence does hear some other noise coming from somewhere in the distance on this level. Power tools, perhaps?