Tris Catt leads a double life. He appears to be an ordinary boy but in
his fantasy life he is also an alien superhero. The underrunners near
his home are an important part of his secret life, secret tunnels known
only to him.
Unexpectedly Tris's imaginary world is invaded by a girl, Winola. She is
strange but gutsy, and so good at joining in his invented game that Tris
doesn't take seriously the menacing character who she claims is after
her - at least, not until they are caught up in a dangerous situation
which threatens both their lives...