The roof was high enough for him to stand up, so Evan, brave but wary, leaned against the trunk and drank in his surroundings.

Despite the rising heat of the morning, the tree house was cool and shadowed, protected by the shallow coppice behind it, beyond the garden fence. A couple of cushions filled with dust and memories lay on the floor, their covers the vivid, geometric designs from a time long before Evan. One had a faded, rusty patch.

And it was dry. No damp wood, just a smell like the banned creosote his father kept in the garage.

The second thing he noticed was the dead bugs. Everywhere. Dried husks of flies and wood lice wrapped in the sticky strings of the thick webs that decorated every corner.

He wondered which children had played here before him and where they were now.

A long, low call disturbed the peace. The boy started. His mother’s voice sounded far away, but he could still detect her irritated tone as she shouted his name.

He peered out of one of the windows. It was smeared with dust and dirt, but he could see enough to know that she was standing by the back door, calling for him. “Evan. Evan.” Sharper that time. She looked straight at the tree house.

He crouched down, biting his lip and stifling an urge to giggle. Grabbing one of the cushions, he lay down on the filthy floor, staring up at the corrugated iron roof and marveling at the way the metal moved in waves.

In the distance, the back door slammed. He wondered if his mother was right that minute making her way down the garden, readying herself to shout at him. He hated it when she did that, twisting her face into someone he didn’t recognize.

He listened to the sounds of the garden waking up. The rustle of an animal in the undergrowth. A chorus of crickets. The low thrum of a flight packed with tourists.

He stretched out his legs and buried the back of his head more comfortably into the cushion. A spark of pain made him sit up again.

Evan ran his fingers along the faded fabric. There it was. Something hard and square inside the lining and its sharp corner had poked him in the neck. He undid the zipper and felt around.

His fingers closed on a box.

Evan pulled it free and stared at it. He had no idea what it was. He had never seen anything like it before.

It was transparent, smaller and flatter than one of those boxes of cereal from a variety pack, and lined with a cardboard insert marked by a reddish-brown thumbprint. He fiddled with it until it opened.

Inside was a black rectangle with two holes in the middle and a spool of what looked like dark, thin tape. The words TDK and D-60 were printed on it. On one side was the letter A. He flipped it over to find a B on the other side.