Teenage girl Ali who's mother is always depressed wants an adventure this upcoming summer and when her aunt Dulcie offers for her to help babysit her little cousin Emma at a lake in Maine she couldn't refuse.

But this lake house isn't any old lake house, Ali's mother and aunt used to practically live there every summer while growing up. But Ali is concerned about going when her mother is stressed about her leaving her. Ali questions herself and wonders why her mother does;t want her to go? Could her mother be hiding something?

Before leaving with her aunt, Ali finds an old photo of her mother and aunt with a face of another girl torn out in her attic. Ali wonders why her mother would do this. She looks for the name of the girl on the back of the photograph and the only thing to be found is a "T". Ali asks her mom about it and she gets extremely upset and does not want to talk about it.

When arriving at Gull cottage at the lake Ali finds some interesting clues about who may be the girl in the picture such as a crayon scratched "Teresa" on now of the old game boards from her mothers childhood. She asks her aunt about it and she gets very flustered at her. While all of this is happening, Emma found a new friend who seems to be a troublemaker. Her new friend sissy is very odd and creepy.

Ali experiences some traumatic events just in the first couple of weeks of being at the lake and she is starting to rethink the adventurous summer she had planned for. The lake was too dreary and cold. Ali learns that the girl in the torn picture was in fact Teresa and she died when her mother was younger. Ali wondered if there was more to the story and she soon had some insidious realizations.

Teresa had a nickname that was "sissy" quincidentally the same name as the creepy girl that was making a bad influence on Emma.

Sissy was wanting the two girls to find out what really happened to her the day that she died and she wanted Ali's mother and aunt to confess about their lies. They are taken on a real adventure one that Ali could never had dreamed of, both Emma and her lives were in danger and they could see the end coming when Emma jumps into the lake for a doll that sissy had been bribing her with . Ali was being controlling in Emma's perspective and selfish. Soon young Emma learns that sissy is not a normal girl at all she is a ghost. All in all there is a great resolution to the problem including finding the lost bones of poor little Teresa Abbot.