A doctor battles his fear of needles to rescue his daughter from a former physician, the source of his phobia, bound to his daughter by blood.

'I would start with the best part of your loglines: When his daughters school is held captive by the man responsible for his sisters death?? (This is very solid)'

I have written exactly that at least a couple of hundred times, but then I get all my possessive pronouns mixed up and I scrap it i.e. "is it the man responsible's sister or is it the doctor's sister?"

But now I've got some backup on that line, I'm definitely using it.

Thanks. This is definitely useful advice.

I decided to go back and review your previous logline attempts:
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"When a school is held captive by the man responsible for the death of his sister, a doctor has visions of a lost childhood revealing the secret between his sister and the man that now threatens his daughter's life."
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"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."
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"A doctor is forced to relive his traumatic childhood in order to solve the mystery that may save his daughter's life."
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The problem is you are presenting some abstract ideas that don't really give us any clue to what's going on.

I would start with the best part of your loglines: "When his daughters school is held captive by the man responsible for his sisters death..." (This is very solid)

The problem is, "Saving his daughter by reliving a traumatic childhood" or "saving his daughter by battling his fear of needles," is way too abstract, it doesn't tell us how does that action saves his daughter.

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"When his daughters school is held captive by the man responsible for his sisters death, In order to save her, a father must give clues to the police negotiator about madman's mindset by undergoing hypno-therapy, reliving a traumatic experience"
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This would explain how reliving a traumatic experience would help save his daughter.

However, my logline attempt is still too long and rough but hopefully you see where I am going with it. I hope this helps.

THANK YOU.
Boiled down, that is pretty much the main? story. I seemed to have been bogged down by the suggestion that a link between the madman and the doctor should be evident in my logline. I already thought it was evident (somewhere) in one of my other loglines, but it seemed to need far more explaining than word count would allow.