They are walking the Cadiz seawall when Chelo tells her boyfriend what she saw on his tab. For a while Javier doesn’t say anything, just stands and looks back toward the beach, where gray waves are crawling to shore on hands and knees. There is heavy fog this morning. When he slid out of bed to run, she told him not to get lost or disappear.

Afterward, while he was toweling sand off his feet on the hotel balcony, his tab buzzed a new email. Chelo knew he was waiting on a contract, so she groped across the bedspread and checked it for him, and it wasn’t the contract.

“Mira la catedral,” Javier says, pointing to the halfway-renovated church finally sliding out from the mist, catching a tardy sun on its spires.

“Preciosa,” Chelo agrees. “And the email?”

“Spam,” Javier says. “Probably it was spam.”

They walk on, peering down over the edge in turns. Giant concrete cubes are stacked along the base of the seawall, breaking the waves below into percussive thumps of white foam. Some pioneering graffiti artists have spidered down on maintenance cables, turning one block into a giant Rubik’s cube, another into a black-and-white six-sided die.

When Javier leans to look, Chelo looks at him. He does not look like her other boyfriends.

Her abuelita pulled her aside to tell her as much in a worried whisper. He’s short, non-descript, and even though he runs he has a gut, swirled with wiry hair. His face is flat, eyes a bit sunk, and his nose is ridged crooked from childhood football. He never played apart from patio games in colegio, though. He is not one of the athletes Chelo usually magnets to.

But there is something that drew her to him the instant they met, in a bar near the engineering campus in Seville. Something about him, maybe in the shape of his hands or his straight even teeth or the sweat-and-soap smell of him.

Chelo shivers without meaning to, and Javier sees it how he always does.

“Cold?” he asks, rubbing his hand up and down her bare arm. It looks like something alien.

“No,” she says, then, unable to hold it in: “It had all your information. The email.”

The instant Chelo says it, she wonders if she’ll regret it. She has been happy for the past two months, a slow, dependable sort of happy, and this is their first trip with just the two of them, fleeing a Seville crowded to bursting for Semana Santa. Here in Cadiz they have the flour-soft beaches all to themselves, and until the email, it was almost perfect.

“It wasn’t spam,” Javier says.

Chelo knew this already. She does have another hope, though. Along with freelance coding, she knows Javier used to deal a bit from his apartment: hydroponic pot, sometimes mushrooms, nothing exciting. But maybe he bought the cupid two months ago to flip it.

“Who was the drug for?” she asks.

Javier’s face twists. His eyes slide away. “For you,” he says.

A sunburned German couple come and ask them, in dictionary-precise Spanish, for directions to the castillo. Chelo can’t speak, but she smiles back at them through aching teeth while Javier explains. Once the tourists are gone and the hook in her lungs has loosened, she asks him how many times.

“Only once,” Javier says, and she thinks he might be looking at the skin between her eyes, a trick he taught her before a job interview at Desigual. “That first night. In La Bicicleta.”

“You put it in my drink, then?” she asks. She wants to hate him, scream at him, but she’s not sure how. She hasn’t done that with him yet. It happened naturally with the other boyfriends.

“No.” Javier’s eyes are wide; he shakes his head. “No. It’s not like that. It doesn’t work that way.”

“Tell me how it works,” Chelo says bitterly.

She watches dirty gulls swoop and circle while he explains, haltingly, about the primer scent and the trigger scent, and how a pheromone is not a depressant and not anything like a date rape drug. Chelo remembers her and her friends sliding into the hookah table beside his, in the smoke-smothered upstairs of the bar, and how she couldn’t stop her head turning his way.

“It’s all the small things.” Javier’s voice is stretched tight. “It’s hedging a bet. It tells someone’s body —”

“My body.”

Javier blinks. “Sorry,” he says. “Your body. You. It told you I’m an ideal chemical match. For genetic diversity, health, fertility. Things that go straight to the subconscious when you meet a person. When you taste them, smell them. It’s not some sort of aphrodisiac. It’s not a love potion.”

Down below, Chelo catches sight of two men in wetsuits spearfishing, an orange buoy floating between them and a cooler set up on the shell-crusted rock. “Then why did you pay so much for it?” she asks. “If it barely does anything.”

Javier winces. “I’m not saying it does nothing. But it’s no different from bulking at a gym. Muscles don’t grow like that in nature, right? It’s to simulate better genetics than you’ve actually got.”

Chelo begins to suspect that he wanted her to find the email receipt, or at least that he’s rehearsed this a thousand times in his head.

“You wear makeup,” Javier says, with a wheedling in his voice she hasn’t heard before.

Chelo clenches her fist on the grimy edge of the wall. “You’re welcome to not fucking look at me,” she says, and the anger feels good, going off in her chest like a flare. “I didn’t get a choice. You drugged me.”

“You drug me,” Javier pleads. “Every time I see you, every time I touch you, it’s the same physiological response. It’s all hardwired.”

“So you can just reach in and rewire me,” Chelo says. “Like stealing an old car.”

“You feel like I tricked you?”

“I don’t know. Yes.”

“Look, Chelo, all the chemical stuff runs deep, but it isn’t us.” Javier pats his chest, where Chelo sometimes puts her head in the night to hear his heart. “I was tricking nature, the way people have always done.” He pauses, trying to hold her hand. She moves it. “I was hedging my bet,” he says, voice nearly to cracking. “You still made your choice.”

Chelo chews the inside of her lip. “It was only once, you said.”

“Only once,” Javier repeats. “I didn’t want to fuck up. Everything I could control, I wanted to go right. Because I knew I wanted to be with you.” He gives her a pained smile.

Something that’s been crouching in the back of Chelo’s mind rises. “How did you know?”

“What?”

“How did you know that you wanted to be with me?” she asks, feeling cold. “And how did you make the primer and the trigger without my DNA? We met the first time that night.”

Instead of guilty, Javier looks hurt. “No,” he says. “We’d met before. On campus. That astronomy course.”

“Bullshit,” Chelo says, raking her memory, but now she’s not sure.

“We did,” Javier says. “And I was crazy about you.” He grimaces instantly and she can tell he wants to reel the word back in, but she doesn’t let him.

“Crazy. Right. So you took one of my hairs, or something.” Her voice shakes. “And you ordered this cupid, and you followed me around like a lunatic until you had a good shot at dosing me?” Tears are welling hard in the back of her throat.

“Isn’t the only difference between a lover and a lunatic reciprocation?” Javier asks.

“You stalked me and drugged me,” Chelo snaps. “This isn’t some fucking telenovela, there are laws and the people are real people and —”

“You really didn’t remember me at all, then.”

“What?” Chelo rubs hard with the heels of her hands, keeping her eyes dry.

Javier’s eyes are shiny, now, but he shakes his head and doesn’t repeat himself. “Would you jump off this wall if I asked you?” he says, pointing out at the fog-caped sea.

“I know that’s not how it works,” Chelo says. “I know it’s not mind control.” She bites back a sob. “But how do I know it was only once? How can I ever know that for sure, now, huh, Javier?”

“I’d jump if you asked.” Javier levers himself up onto the edge like he’s posing for a photo. “That’s the difference.”

Chelo feels a numb panic. “Get down,” she says. “I would never ask that.”

“But if you did, I would.” Javier is crying now, tears tracking down his stubbled cheeks. “And I knew that when I used the cupid. I knew you would never love me as much as I love you. But that’s okay, you know? Two people can never love each other equally.”

Chelo has never seen Javier cry, has never even thought of it. Javier is quiet and steady and watchful, but now she wonders if that was him at all, or if it was some clamped-down, modulated version of him. Whatever he knew she would like best. Whatever could hedge his bet.

She’d felt happy with Javier, happier than she had in a long while. Maybe he really did only use the cupid once, and maybe the drug really had done nothing the weed or alcohol wouldn’t have. But now, even if she tries to forget, things won’t be the same.

Chelo looks at Javier, his imploding shoulders and hanged head, and she knows her friends and family will not ask too many questions. They never thought she and him looked right together in photos. It makes her suddenly furious, at Javier, at herself, at everyone else.

“What if we both jump?” she says, but instead she goes to the wall and sits there with him, not quite touching. Enough mist has cleared that they can see construction cranes behind the cathedral, poised like tentative birds. The space between their hips, between their splayed hands, is wide as the sea.