1.10 "Asylum" is literally just an episode all about Dean being smart and perceptive as fuck.
He finds a hidden journal in a false wall.
He reads the journal and uses it to unravel the entire narrative of the haunting by himself before meeting up with Sam again.
He determines what likely happened to Dr. Allicot (killed by his patients in his own torture room).
Based on that hunch he finds the hidden torture room in a room Sam had already checked.
He tricks a ghost-influenced Sam into taking his unloaded pistol so he can get the drop on him and knock him unconscious.
He notices Dr. Allicot's hair sticking out of the side of a cabinet and uncovers his body.
While Dr. Allicot is actively attempting to infiltrate Dean's mind, despite the fact that he very much does have hidden resentments/anger, Dean resists long enough to torch Dr. Allicot's bones.