A beautiful door.

Dark, heavy wood, early twentieth century. It somehow belongs with the muted, hollow sound of his knocking that fills the rounded stairwell, echoing off the slightly too steep steps, the high and elegant ceiling, and the flowery wallpaper that grows more lushly realistic on every floor. Ewert Grens, standing in front of an apartment in central Stockholm, knocks again even harder.

“Somebody’s in there. I hear them all day long. I hear it through my living room floor, in my hall, even in the bathroom. You wouldn’t believe how thin the walls are in this building.”

A voice, pinched and irritated, comes from behind him. Grens doesn’t turn around, doesn’t answer, just rings the bell for a fourth time.

“Someone’s singing—probably one of the kids, I’m fairly certain they have three. And I think it might be a TV too, very loud. It’s been on for at least a couple of days. And not during the day—all night, too. I was the one who called, I live in the apartment upstairs.”

The detective superintendent finally glances behind him. A man, just over forty, arms crossed, the kind of guy he dislikes immediately without really knowing why. The type who puts their ear to the door and listens.

“Happy birthday.”

“What?”

“That’s the song the child sings. Happy birthday to you. Over and over.”

The neighbor called in about the strange sounds. And called again when strange sounds turned to strange smells.

“I’m going to have to ask you to return to your own apartment now.”

“But I’m the one who . . .”

“Yes—and you did the right thing. But now I need you to go back upstairs so I can take care of this.”

Grens waits until he’s completely alone before knocking a third time, impatiently, urgently, as if the muted and the hollow are calling out decisively. When no one opens the door, he bends down to peek through the mail slot, but before he gets there, someone on the other side tries to turn the lock. They don’t manage, but they try again. He can hear a quiet thump on a hardwood floor.

“Police.”

Thump, thump, like someone jumping.

“Police. Open the door.”

A lock that is slowly being turned. A handle that seems to move on its own.

Ewert Grens doesn’t like using a weapon. But still he grabs the gun from his shoulder holster and takes a step back.

Her hair is quite long. Blond. He doesn’t know anything about children, but if he had to guess—she’s four, maybe five years old.

“Hello.”

She’s wearing a red dress. Big stains on its chest and stomach. She smiles, her face is also stained, maybe from food.

“Hello. Are your mom or dad at home?”

She nods.

“Good. Can you go get them?”

“No.”

“No?”

“They can’t walk.”

So strange.