With an entire school held captive, a doctor must relive a traumatic childhood that may solve the mystery behind the sadistic madman that threatens his daughter’s life.

Thanks, quite helpful. I think I've got it, but I'm still playing around with different ways of saying specific words and hopefully will be able to bring the word count down a bit before posting my next (hopefully final) revision.

glad to se That May" got cut.

I like the general concept, but I'd agree with the others here in that 'relive a traumatic childhood' feels vague, and slightly passive. It's difficult without knowing the entire story, but does this help?

"When his daughter's entire school is held captive by a sadistic madman, a doctor realizes that this is no random event, and that the key to their survival lies deep within his own traumatic childhood."