You cast your Spell.
With your new-found strength you leap easily to the
centre of the room over the trench and break open the lock on the chest.
You curse as you find nothing inside but a good weight of lead shot.
Quickly, you leap back across the trench towards the other door, as the spell is wearing off.
If you are lucky you make it safely across.
If you are unlucky you fall in the trench.