In the movie's prologue, Crowe is shot and killed by a deranged former patient. Thinking he survived the gunshot, the ghost of the doctor just goes on with his normal life. He meets an especially troubled kid named Cole (Haley Joel Osment), the product of a broken home whose favorite hobby is hiding in churches and whispering Latin to board game pieces. Cole has mysterious cuts and bruises all over, and claims to see dead people (which, unbeknownst to Crowe, is the only reason the two of them can communicate).
The movie then shows us what a great, empathetic psychiatrist Crowe is, even in spirit form. Making a strong connection with Cole almost immediately, Crowe becomes Cole's voice of reason and sanity, going far beyond the call of duty to provide him with stability and advice and help him come to terms with his gift (or curse, as the case may be).
But Wait a Minute ...
The fact that Crowe can't talk to anyone but Cole is ... a fairly big problem here.
Perhaps he has always communicated by writing on fogged glass.