It begins with an innocent request. One unremarkable winter morning, civil servant Richard Eusden is on his way to work in London when he is intercepted by his ex-wife, Gemma. She has sad news of his old friend, her other ex-husband, Marty Hewitson. Marty is dying, but needs one last favour done for him – now, today, at once. Eusden reluctantly agrees. But what should be a simple errand soon it...