A doctor is forced to relive his traumatic childhood in order to solve the mystery that may save his daughter's life.

Could you perhaps give an example of how his daughter's life could be in danger that would help to answer your question?

The way I see it currently is - the key to the mystery is in the doctor's childhood and if the mystery isn't solved then his daughter dies.

I thought it was all clear, but then, it's my idea and I have more details than the casual logline reader does.

This is too vague and there's a disconnect with the two halves of the logline. How does reliving his traumatic childhood save his daughter's life? I think you have to hint at why his daughter's life is in danger.

This is interesting. You have my attention because I'm wondering exactly what will he go back to see that will help.