Death needs a do-over.
Azrael---angel of death, grim reaper, destroyer of worlds--messed up. Instead of taking Molly Molloy's soul, he patted her on the back and saved her from a chicken wing and now she can see him. Talk to him. Touch him. Say 'no' to him. And worst of all, make him question.
The Powers that Be are impatient with him to fix his mistake but before he can, Death makes one more.
He falls in love.