Imaginaerum tells the story of an elderly composer, Tom, who suffers from severe dementia. As he has had the disease for years and has regressed into childhood, he remembers practically nothing from his adult life. His music, friends, all his past including the memory of his daughter are a blur in his fragile mind. All he has left is the imagination of a ten-year-old boy. As he drifts away into coma, it seems impossible to get back what he has lost. Tom travels through his imaginary world seeking answers and finding memories, while his daughter, Gem, tries to recover the bond she had once shared with her father in the real world. As they have become more and more distant from each other over the years, and as there's even greater obstacles separating them now — Tom's coma and his imminent death — Gem's project feels doomed to failure. However, through Tom's darkest secrets, Gem discovers the path she must follow in order to find her father again.