In her late twenties, Alba moves back to her hometown, Porto, for a dream job. She is drawn towards an area of the city near a famous lighthouse, though she isn't sure why. Even though she has had some health difficulties, including surgery to replace her leg with a bionic limb in childhood, her life is good: she has a circle of friends and a close family.

But she feels empty. Something is missing and despite all she tries she can't figure out what it is. The last time she remembers feeling fulfilled was as a child when her family hosted M, an AI-prototype, who became her companion. At the time she unexpectedly lost M her hollow feelings grew. She longs to find something she lost in her life and believes that M can help.

Briefly, a love affair with a fellow scientist fills her emotionally, but when tragedy strikes, she realises that she needs M more than ever. When M mysteriously returns to her, she discovers that everything she believed about her life has been wrong, and there is only one course of action to bring her back to wholeness. But she doesn't know if it is too late.