P er the usual routine, I stepped behind the curtain that night ready to coax Río out of his corner. Instead, I found him propped on the glass rim and peering down at me like I hadn’t held up my end of a business agreement.

“I expected you earlier.”

Climbing up the tank side to resume my seat was a little trickier with a lamp in hand and a newspaper bundle under my arm. “I didn’t think you were the waitin’ type.”

“There is naught else to do in this cursed cage but wait,” he grumbled, flicking away an offending bubble.

“Hopefully, you won’t mind so much when you find out what kept me.”

Río’s eyes livened as I unwrapped the newspaper and held its contents up to the lamplight. “Snapper,” he gasped. “Where did you catch it?”

I fit it through the lattice and let it fall into his open hands. “At the Clarendon. If by ‘catch’ you mean ‘bribed el camarero .’ Buen provecho. ”

He melted like I’d just dropped a bouquet of roses through the grill, then tore into it with startling gusto. As much as watching Río finally enjoy a meal was a balm on a shitty evening, I thought he deserved better than snapper to soften the news I was about to give him. I didn’t think he’d be too pleased about my sudden promotion—even if the extra cash it put in my pocket had paid for his meal.

“Morgan’s leaving for a while, so he’s put me in charge,” I began. “Says I’m supposed to look after you.”

Río regarded me askance. “Have you not been doing this already?” he asked through a bite of fish. “A barnacle could not look after me with as much tenacity.”

Abashed, I took off my cap. “Means I’ve got the key to your tank.”

My turn to wait for him. When he finally spoke, it was barely above a whisper.

“You cannot free me, can you?”

Don’t ask me how he was still floating. If it were me finding out the key to freedom wasn’t enough to liberate me, I’d have sunk like a stone.

“Not on my own,” I murmured. “And after what happened tonight, I’m not sure I could get anyone here to help me if I tried.”

“What happened?”

I chewed my lip and tried not to bite through it. “They don’t know what to do with us. On one hand, they’d celebrate if you left, they’re so sure Morgan’s trying to replace them. On the other: the park’s in trouble and they think you can save it for ’em. As for me? Soy un extranjero. ” I balled up the newspaper and flung it as hard as I could over the side of the tank. “Even around a bunch of foreigners, I’m too foreign.”

Río’s expression went gray. “Perhaps you should seek a better harmony.”

I had a hunch he wasn’t talking about music. “What’s a ‘harmony’?”

“To you? A bunch of foreigners,” he said dully. “‘Harmony’ is how we refer to our family groups.”

No one who’d ever heard a merperson speak could deny it was the perfect phrase. “A harmony of merfolk,” I said, amused. “That’s got a much better ring to it than ‘a school of fish’ or ‘a murder of crows.’”

“‘A murder of crows’?” Río made a disgusted noise. “Drag me on a reef, but humans are vulgar!”

“What about yours, then? Where’s your harmony?”

There was a pause when it seemed Río wouldn’t answer, which I quickly realized was his only sensible option. Río would never risk his kin by telling a human where to find them, whether or not the human was me. I was about to take the question back until, surprisingly, he spoke.

“With my mother returned to Neptune’s robes, I am all that is left of it.”

My heart foundered at the stoic restraint with which he spoke such awful words. “ Perdóname. I shouldn’t have—”

“It was inevitable,” he said in an empty voice. “Our race only persists, it seems, out of sheer stubbornness. We have been dying off for centuries.”

“Dying? But you seem so...” I took in his strong, sculpted frame, and felt my cheeks burn. “Sturdy.”

“Ocean water is life-giving and ages us far more slowly than our earthbound cousins,” he explained, rubbing absently at the scar over his eye. “But changing seas have made us vulnerable. Most harmonies have fled to the deep or taken refuge in other waters. The kind without large fishing nets or steam-powered ships turning the tides to acid.”

“The East River seems like the worst place in the world to dodge a net,” I said. “What were you even doing there?”

“The East River is not a river at all, but a saltwater estuary.”

“You didn’t answer my question.”

Río exhaled, caught out. He laid back on the water and gazed past my face at the metal rigging above us. “I struggle for words, Benigno,” he said softly. “I have followed the Currents all my life. Of late, I have wondered whether they have failed me, or I have failed them.”

“‘Followed the currents’? To where?”

“Not where.” He touched his mouth as if it could summon the right words. “The Currents are the wisdom and intuition of the living tides. Guidance for all water-bound souls.”

“Wait, you believe the water is... alive?”

Río’s fingers swept delicate figure eights through the ripples. “Your skepticism is human. Your kind worships your individuality, injuring yourselves in the delusion of being separate from each other and the world,” he explained without his usual snobbishness. “The children of Neptune live as waves on the water—unique and separate only in appearance, for we are united in spirit by the vastest element on earth. Thus, when the Currents call, we obey.”

Waves on the water. The way his sharp eyes softened as he spoke those words wrought an ache in my chest that didn’t feel like asthma.

“Except I misinterpreted them, I think,” he continued. “I might never have approached the woman in the boat otherwise.”

“You mean to say you towed Sonia back to shore because the Currents told you to?”

At this, Río’s eyes closed like he was forcing himself to think through a bad headache. “You ask why I was in the East River. Perhaps you know of the tragedy that occurred there.”

“A tragedy,” I said, then instantly knew what he was referring to. “You mean the General Slocum ?”

When his eyes opened, they stared out at nothing. “My harmony was larger then,” he said. “A dozen of us saw the ship succumb. Watched as the humans aboard it—women and children, mostly—cast themselves to the water wearing garments too heavy to float, hoping to spare themselves from burning alive. We felt the calamity at hand before we had even broken the surface, but the Currents’ ache was so great, we knew not what to do.

“Our elders had taken it as confirmation that humanity would be frightened into violence if we interfered, having long decided that to save humans from themselves was to advance the destruction of our race and our home. After all, choirs of harmonies had already heeded the instinct to swim deeper, to migrate to the farthest reaches of the Atlantic lest we find all merkind obliterated on the tip of a harpoon.

“But the horrors would not leave me. Human screams rang in my ears like whistles long after the vessel surrendered to the estuary. When I could not withstand my guilt at letting them drown, my mother alone sympathized. A mermaid from the Tailfin Sea—what your kind call the Caribbean—she believed in human virtue and perceived a different warning in the Currents’ ache: that we too would find ourselves lost—extinct, even—if we abandoned humankind.”

I sat on the lattice, dumb with shock. Not only because he’d witnessed the worst maritime catastrophe in New York history, nor because Río’s kind had stood by and let it happen—but because, by the looks of it, his elders’ fears were justified. He and his mother had believed humans deserved saving, and humanity had punished them cruelly for it.

“The harmonies fled the estuary that day. But I chose to stay, and so,” he concluded, “my mother stayed as well.”

As he finished his story, my mind assembled another. Of a merman who finally found someone to rescue on a cold moonlit night, and the mermaid who wouldn’t let him do it alone.

“Río, you don’t blame yourself for her murder... do you?”

His eyes went red-rimmed and wet. He draped a webbed hand over them. “Out of seawater, I cannot learn what purpose has killed her and driven me to this prison, except that my foolishness is to blame.”

It dawned on me, perched on the metal bars with a clear view of Río’s crisis of faith, that we were going through the very same thing.

“Oye,” I said, “your mother died because Morgan killed her. As for the rest, I don’t know the Currents, but I know what it’s like to get pulled somewhere by something you can only know by how strong it tugs. Sounds to me like, when the Currents got muddy, you followed your heart, and that’s gotta be the same thing. It’s what got me from Puerto Rico to Nueva York .”

He sat up in the water. “What did the Currents say that made you abandon your homeland for a shore so far away?”

The truth found its way to my mouth—in Spanish—for the first time in four years.