There is a garden, a beautiful and unlikely place where pine trees grow next to eucalyptus and polar bear cubs and tiger cubs play together. In the centre of the garden there is a tree, gnarled and twisted and immense, where apples grow red as rubies. A man is standing below it, on tiptoe as he reaches to pluck an apple. He looks twenty perhaps, or a little younger, only just a man rather than a boy. The apple proves harder to pull down than he hoped and he curses as the branch bobs up and makes him stumble. Finally the apple comes away in his hand. It smells of autumn, crisp and clean, the scent of things dying a beautiful death at the end of the year.

'What are you doing?' asks a voice. It is a man's voice deep and rumbling, but the creature asking is not a man. It has a man's body, squat and deep chested, almost hidden behind two draped wings, another two wings rise above it. It has four heads, a lion's, an eagle's, an ox's and a man's, with the man's head in front staring at the intruder. It is a terrifying sight and the intruder is afraid, but only as someone caught where he shouldn't be by someone stronger than him, and he drops his gaze sheepishly with both hands still clutching the apple.

'Sorry,' he says.

The cherub shakes its heads, one hand scratching its lion's mane. 'I am to stop humans entering the garden lest they become as gods,' it rumbles. 'But you are already a god.'

'I know,' says Loki. 'I just thought it might help, I suppose.'

'Knowledge of good and evil,' says the cherub. 'Do you not already know?'

Loki leans back against the tree and holds the apple up as if he might be able to see the sunlight through it. 'Do you?' he asks.

'I am not a god,' says the cherub. 'I need only to obey.'

Loki nods. He's fidgeting with the apple, passing it from hand to hand, until a nail pierces the skin and the scent is suddenly overwhelming. Sun and grass, earth after rain, crushed leaves, fresh apples, clear water. And underneath it all something sharp and metallic.

'This apple smells of blood,' says Loki dubiously.

The cherub shrugs, an impressive gesture with four wings and four heads. 'It smells of many things.'

Loki sinks down to sit cross legged under the tree, apple clasped loosely in his lap. 'Is knowing a bad thing?' he asks. 'I always get into trouble for not knowing.' He tentatively puts one finger to his lips and catches a drop of juice on the tip of his tongue, going cross-eyed as he tries to watch himself lick it. 'I don't feel any different,' he says after a while. 'I suppose I'd have to actually eat it.'

'Yes,' says the cherub.

'I've eaten Idunn's apples,' says Loki looking up at the sky. 'They're more like the other ones. The ones you're actually guarding. Or would be if you weren't standing here watching me.'

'I am still watching the tree of life,' says the cherub calmly.

'You do have eyes in the back of your head,' agrees Loki. He pauses. 'What would eating this actually do to me?'

'It should do nothing to a god,' says the cherub.

'Somehow I'm always the exception,' Loki mutters. He stands up and eyes the cherub warily as if he still expects to have the apple taken from him. 'You won't stop me taking it out of the garden?'

'Even if you gave it to a human it would make no difference now. That is not the tree I am guarding.'

Loki looks at the cherub and blinks, seeming suddenly to come into focus. He looks less a young man now and more an animal, sharp as a cat watching a mouse hole. 'You came over to see what I was doing because you were curious,' he says. 'And I thought angels had no free will.' He takes a step closer, eyes reflecting something more than sunlight. 'Have you ever wondered what it tastes like? What knowing good and evil would be like?'

'You are not a man. You are a serpent,' says the cherub flatly, wings spreading as it speaks.

But Loki is already gone, a bright hawk darting from the garden with an apple clasped in its talons and trailing juice.