Sure thing, here's the gist.
Cause and effect of all sorts in ARIS is done with locks. In this case you want to apply locks to the triggers (locations) that point to your plaques. Say you have plaque 1 and plaque 2. You want p2 to show up when p1 is viewed and p1 to disappear when p1 is viewed.
The lock you put on the trigger for p2 is
player has already viewed p1
The lock you put on p1 is
player has not yet viewed p1
In the manual I describe the logic of this more thoroughly, and use a metaphor of keys and pins on keys to describe some of the complications you can come up with. The basic idea is that when you create a lock, you specify the key (what unlocks the lock). Whenever that statement is true, the lock is unlocked.http://manual.arisgames.org/editor/locks
Give that a go and see how it goes