It was dirty, punishing work, moving out of water, though the stairs brought back fond childhood memories. Until then, it had had no plan, only out, but the dirt and the memories brought the plan: return to the sea.
There were only a few thousand problems with that – the number of bodylengths it was away from the sea, and the means of getting there.
The salmon refused to get discouraged. After all, it had already been caught, gutted, frozen, sawn into pieces, thawed, sold, and left in a fridge for days. 'No sense crying over spilled milt', it thought.
It searched the basement, found the door and the locks, and, leaping up, opened them.
It pondered. It of course knew instinctively where the sea was, since all salmon have GPS built-in so they can return to the places of their birth. But the idea of hoofing it all the way to the sea didn't appeal to it. Too long, too dirty, too dangerous, no hooves.
It flopped down the road, pondering more, until it came to a road with cars driving on it. Huge cars, roaring past. The salmon contemplated trying to hitch a ride on one that stopped at a light, but the truth is they were too big and terrifying, and there was no way to control which way they would go.
Then, miraculously, a late-night college student came home, riding a bicycle, and the salmon was inspired. A bicycle! Not too big and scary, well except for the too-big part, and simple enough for a salmon to understand.
It returned to the basement it had left, and sure enough, there was a bicycle.
Now, if you're unfamiliar with salmon, you might discredit it when I tell you that the salmon shrank the bicycle to fit it. But consider: it has GPS built in (everyone already knows that). And what is GPS? GPS converts a position on the globe to a position on a small manageable map – in essence, shrinking a macrocosm to a microcosm. As such, GPS in a salmon is just a particular use of a more general adaptation, namely, the ability to shrink things if said shrinking helps the fish to get to where it wants to go.
And so, to make a short story short, the bicycle shrank, and the salmon got on and did its best to imitate the student that had passed by. It turned out to be harder than anticipated, but in time the salmon was on its way. And as the sun rose the next morning, the old, exhausted, gutted, sawn, frozen, thawed, dirty, sold fish dropped its bicycle, and slipped into the cool welcoming waters of the bay.
'Wait!', cried the bicycle. 'Take me with you!'