Everyone has secrets. What extent will the people of Splendid Harbor, NH go to keep their secrets from becoming known? Worlds will be rocked and someone will die as each unveiled secret brings up darker secrets from a prominent family's past …

This really isn't a logline. First you have multiple sentences..a no-no. And you ask a rhetorical question. Another no-no. You need to share who the antagonist and protagonist are and what is the conflict.

Consider this, When the dark secrets of a prominent family of Splendid Harbor are unveiled, more lives are at stake unless the returning grandson can stop the blackmailer from revealing more of the family?s twisted past."

YOu have to give at least the who, what and why. Is there one event that sets them all on edge and the story reveals their secrets? The the town is the protagonist and whatever/whoever sets them all off is the antagonist. What do they have to lose? Why should we care? Who are these people. Who cares if they are rich or poor if that's all they have. The place is pretty immaterial, unless it's unique and, unless that's the protagonist. There have been films like that, but I can't think. Sorry. Could be really great, this. Keep at it.

Although this creates mystery and some sense of wanting to know what the secrets are, I feel that you need to give more information to grab our attention.

For example, all I really know from this logline is that the story is set in Splendid Harbour and 'some rich people' have 'some secrets', but as you state in the first line 'everyone has secrets'.

I am sure that you have a great story in your mind, full of twists and turns, but I suspect you are being overly secretive yourself for fear of revealing the twists, so much so that all you reveal is the location!