plastered to the hairline??
The first time I laid eyes on Terry Lennox he was drunk in a Rolls-Royce Silver Wraith outside the terrace of The Dancers. The parking lot attendant had brought the car out and he was still holding the door open because Terry Lennox’s left foot was still dangling outside, as if he had forgotten he had one. He had a young-looking face but his hair was bone white. You could tell by his eyes that he was plastered to the hairline, but otherwise he looked like any other nice young guy in a dinner jacket who had been spending too much money in a joint that exists for that purpose and for no other.
I would like to know what does "plastered to the hairline" here mean. Thanks.