Would you risk your life for a stranger? Would you place yourself in mortal danger on the moon? Hadrian Wall did. When Grior from Jupiter materialised in Hadrian’s bedroom in the middle of the night, little did they know of the adventure that would follow.? Grior has lost his bag of interplanetary travel crystals on Earth’s moon, during a fierce battle between the friendly Dugiri and the vicious Zapro army. He just had time to bite the Earth crystal, ingest travel gunk, secrete two travel pods and the remains of the moon jewel in its pouch and dematerialise, before the bag was snatched. He cannot return home without the Jupiter Gem, which is in the bag stolen by Lantar, the Zapro leader. The Zapros lurk on the dark side of the moon, preparing to colonise the Earth. Join Hadrian in his perilous quest and share in the shocking secret he unearths while on the moon.