Twelve-year-old Jodie Jackson lives with her father above their family boatshed in Serpentine Bay in Sydney Harbour. She attends a new school, where she is faced with bullying and loneliness. She is also feeling grief at the death of her mother the year before. She misses her mother and wonders where she is now.

Her father is consumed by his work and won't share his emotions with Jodie, so she takes solace in sailing her boat around Sydney Harbour. Her favourite spot is Lighthouse Point where her family used to go for picnics. Her father refuses to go there as it brings up memories, but Jodie likes to feel that she is connecting with her mother.

She makes new friends with Sarah Chan and together they explore the derelict lighthouse and Jodie finds an old photo of a girl. The ranger finds them trespassing and they discover that there are plans for the area to be turned into a marina and a restaurant. Jodie is horrified.

The girls find some dead penguins floating in the water and later Jodie finds a live penguin living under the jetty on a nearby island.

One night her mother appears in her bedroom and takes her with her to Heaven World and shows Jodie what a lovely, beautiful light-filled place it is, and how happy she is being there, and that she is always watching over Jodie. She can't wait to tell her father about seeing Mum, but he dismisses it as just a dream and walks away.

Jodie is angry and sails her boat out into the Harbour despite the storm warnings. She capsizes but manages to swim to shore and seek shelter in the derelict hall on the nearby island. A girl appears looking for her own mother, and Jodie realises it is the girl in the photo that she found, and Jodie tells her to go towards the light that is shining through the trees.

Her father finally rescues her and is distraught by the thought of losing her. He tells her he loves her and vows to be more open with her and talk about his feelings and their shared loss.

The rangers at Parks and Wildlife investigate the area and discover a new penguin colony living in the bay, and the plans for the lighthouse are shelved.