It was the first perfume to contain genuine human pheromones. “Be irresistible,” said the commercials. “Give in to temptation.” They called it: S.E.X.

Very original.

S.E.X. was a hit. It flew off the shelves. Manufacturers couldn’t keep up. There was something . . . alluring about it.

“It’s like a bubble bath strewn with rose petals.”

“It’s like champagne in Paris.”

“It’s like chocolate mousse on Valentine’s Day.”

Amorphous, the fragrance adjusted to your body chemistry, so that no two people described the scent the same way.

“It’s like taking a long walk on the beach.”

“It’s like a spring meadow on a starry night.”

“It’s like a cheery fireplace on Christmas Eve.”

Supposedly, it attracted your perfect mate. One sniff, and you could tell if you were compatible.

I know it sounds crazy, but it actually works. It’s how I found my boyfriend, Mark. He smelled crisp, and musky, with a metallic tang I couldn’t quite place. In fact, I didn’t find a name for it until we moved in together a year later.

We were trying to move a couch into our apartment. I was at one end, and he on the other. Halfway up the stairs, my hands slipped and I dropped the couch. A loose staple caught on my arm, leaving a jagged cut behind.

I hissed through my teeth, watching blood well.

We took a break and Mark patched me up, as gentle as always. When the cut was clean and wrapped, he bent to kiss my forehead. His familiar fragrance comforted me, and it lingered even when he left to deal with the couch.

Strangely, the scent didn’t fade.

I didn’t realize why at first. It was only when I gathered up the paper towels Mark had used to clean my wound that I understood.

It was the smell of blood.