Charlie spent the better part of a month coming up with his escape plan. The only way he would ever be able to give the guards the slip was if he was outside the prison.
He got the idea from listening to the radio. The presenters were talking about healthcare costs, specifically the costs of imaging done on the body like x-rays and MRIs.
He had an MRI done on him once before shortly after he got arrested. They wanted to scan his brain to see what was going on inside his head. It had been entirely the psychologists' idea.
During the MRI, Charlie's hands and feet had been bound with zip ties so he couldn't escape. Handcuffs wouldn't have worked because metal can't go into the machines. If they did that again, it would be simple to escape.
He had picked up how to get out of zip ties without a blade from another inmate during exercise time back when he had a little more freedom. Picking all of those fights had been a bad idea in hindsight.