Back then, no one had known exactly what Lucas had bought that final morning, so no one had known anything was missing.

But now I had the store’s record of the purchase, and we laid it against the inventory, item by item, and the arithmetic came apart in my hands.

The spare adult flotation vest was not on the list of recovered gear.

And one of the orange emergency whistles — four had been bought, one for each boy, and a spare — was missing too.

Two safety devices, bought that morning, that never came home from the lake and were never found in the water.