I like it as well! I think that the dead space without anything there, along with your intent focus on something we can't see makes the photo very eerie, and unsettling... but in a good way, if that makes any sense.
Excellent; this is one of the very, very few images I've seen here where not only is negative space used to great effect, but having the subject staring away from the camera at an unseen subject is perfectly executed. Great job!