But Joyce takes a step back, her palm still extended.

“Buffy,” her mom says again. “Give me the staff. The Marnoxon gem is too dangerous for a teenager to wield.”

The Slayer’s heart sinks. She keeps her grip on the staff firm, holding it across her body like a shield. Her body stiffens, remembering its former defensive posture.

“My mom doesn’t know anything about magical objects,” she says, edging backward. “If it’s not an indigenous fertility mask, she’s not interested.”

“Excuse me for taking an interest in your life. As the mother of the Slayer, I’ve had to learn more about the occult,” the creature that looks like her mother says in a decent impression of Joyce’s exasperated laugh.

“You’re not my mom,” the Slayer says, bending her knees and preparing for an attack. She doesn’t know if it’ll come dead-on or from behind, where the monks lie dormant, but she knows now that she walked directly into a trap. Shame at her own stupidity makes her antsy to punch something. “My mom has no idea what a Slayer is. Much less that I am one.”

“You never imagined that I’d find out?” the Joyce impersonator says. “You thought you could keep it a secret from me forever? While you go out every night and come home bloodstained? While you use the Marnoxon gem to slide from reality to reality, wreaking havoc?”

“Well, now I know you’re not my mom,” the Slayer says, wetting her lips. “Even if she did know about the supernatural, she definitely doesn’t know about portal travel. I didn’t even find out there was more than one dimension until I got thrown out of mine.”

“Well, maybe if you’d told her there was a way out of this world,” the fake Joyce says, a vicious smile pulling up the corners of her mouth, “she’d still be alive.”

Without warning, without sparkly light or magical preamble, the Slayer’s mother transforms into a girl, younger than the Slayer. In a fuchsia Limited Too T-shirt and a cocked hip posture that screams middle school, the girl flicks her long brown hair over one shoulder.

“Who are you?” the Slayer asks.

“Oh, like you don’t recognize your own sister?” the girl says, crossing her arms over her chest. “Real funny, Buffy. Ha-ha.”

The Slayer gives an apologetic wince of nonrecognition. “Sorry, whatever you are. I can see you’re trying real hard to get under my skin, but I don’t have a sister. I mean, look at yourself. Could you look any less like me? Brown hair? Blue eyes? And you’re at least three inches taller than me.”

“You really think you’re pulling off a natural blond? Give me a break.” The fake sister snorts. “I’m your sister. Dawn. Dawnie? Little bit? I steal your clothes and read your diary and follow you around when you do Slayer stuff. You rescued me from a gang of dancing demon bears? And an evil ventriloquist dummy? Come on, Buffy! You know me!”

“I really don’t. The dummy rings a bell, but you? Not so much,” the Slayer says. “Maybe this dimension’s Slayer has a sister, but that’s so not my backstory. I’m an only child. Practically prototypical. Spoiled rotten, custody battle, trouble with authority. You’ve got me all wrong.”