I agree with Adopted Axiom about some ideas, but you absolutely need some of the information from the second half. Without it you only have the inciting incident.
"When a mental patient's artwork links him to the murder of an innocent girl, a (flawed - aloof, perhaps, if his level of experience is the flaw? Maybe arrogant?) psychologist must prove his innocence ..."
The problem I have is that proving his innocence become vague, and the plot could either revolve around a court-room procedural, where the information just needs to be presented to prove his innocence, or else, the psychologist must seek out some "boon" (the piece of evidence that proves his innocence). If this takes place in the real world, specify that. If this actually takes place in the mind of the un-treatable patient, mention that.
Also - prove his innocence to whom? The stakes are much lower if it's just the asylum's board of trustees, than say if it's the police. What if the person murdered was the child of a government official? Suddenly he has the strength of every government agency in whatever country he's in coming down to bare on him.
The hook is good, the need to escape prosecution for a crime he didn't commit works, but you need to clarify what your story is actually going to LOOK like.