Nervous four-year-old Marco, not having any real friends, spends time with his imaginary friend Polo. Together, they set out on make-believe adventures from the safety of his bedroom. At first, Marco sees how the outside world and other kids could be dangerous and scary, but as the years go by, Marco begins to doubt that his so-called safe life with Polo is worth it. This forces Polo to take matters into his own hands and show his true self.