The Military Police Division was thinly staffed, with nearly every officer sent out to investigate the dance girl murders. The main hall on the ground floor was quiet and sparse.

In one of the interrogation rooms, a man was examining a set of big-headed doll props.

“That’s right — these are the ones stolen from our troupe. So that we wouldn’t mix them up with other troupes’ props, we carved a mark on the inside of each doll head. Right here.”

Bai Jin took the large doll head and stuck his own head inside to have a look. Sure enough, a line of small characters read: Xia Xing Performance Troupe.

“How many of these doll heads does your troupe have in total?” Bai Jin raised his camera and took several photographs of the inscription.

“Twenty-six, all stored in the warehouse normally.” The man continued, “Props are always counted before and after each performance. After the show that evening, I sent someone to do the count and found four of the big-headed dolls were missing. It wasn’t necessarily a serious matter in itself, but since the warehouse had been broken into more than once before, I reported it to the Public Security Office to prevent further losses down the line.”

“Thank you for your cooperation. If you could sign here — once this case is resolved, we’ll return the dolls to your troupe.”

The man waved his hands hurriedly, alarmed. “No, no — please don’t. They’re evidence now, so the Military Police Division may handle them as you see fit. There’s no need to return them.”

The doll heads were stained with blood. Even if they came back, they were tainted objects now — he neither dared to take them back nor wanted to.

“Very well then.” Bai Jin understood the man’s reluctance and didn’t press him. “I’ll see you out.”

Bai Jin walked the performance troupe member out and was just turning back when he spotted Yan Qing coming in. His face broke into a delighted grin. “Sister-in-law? What brings you here?”

“Where is Shi Ting?”

“Seventh Brother is in his office.”

At that moment, Shi Ting was in his office reviewing photographs from the crime scenes. When he heard the knock, he didn’t look up. “Come in.”

Then, as though sensing something familiar in the air around him, Shi Ting raised his head from the pile of photographs.

“I’ve made a new discovery.” Yan Qing was already at his desk in a few quick strides, her bright eyes shining with barely contained excitement. “Come to the examination room.”

With that, she reached out and took Shi Ting’s hand, pulling him along.

When Bai Jin saw the two of them walk out hand in hand, he couldn’t help but stare. Were they really so intent on displaying their affection that they even had to hold hands just to walk somewhere?

Yan Qing, for her part, hadn’t noticed how intimate the gesture was — she was simply too excited and wanted to share her discovery with Shi Ting as quickly as possible.

Shi Ting let himself be pulled along without a word. The corner of his mouth curved up ever so slightly.

In the examination room, Boba’s body still lay where it had been left. E’Yuan stood nearby, holding a notebook and writing something down.

“Master?” E’Yuan set down the pen. “What brings you here?”

“E’Yuan, turn the body over.”

“Right away.” E’Yuan quickly set the notebook aside, came over, and turned the body.

Yan Qing produced a hairpin from somewhere and held it up beside the numbers carved into the back of the body, tracing her movements along the figures. “Look — doesn’t the mark the hairpin makes match the wounds on this body?”

Everyone gathered around at once.

“The wound left by a hairpin is different from that of a sharp blade. Because the hairpin isn’t particularly pointed, some areas would have needed to be traced over more than once — for instance, wherever a stroke changes direction. The skin around the edges of the wounds also shows very small, curled-up flaps of tissue, caused by the hairpin’s sides not being sharp enough. Taken together with the depth and width of the wounds, I’m confident: these numbers were written using a hairpin.”

E’Yuan studied the numbers on the body, puzzled. “But isn’t a hairpin something only women use? Could it have belonged to the victim?”

“No. I said before that the instrument used to write these numbers belongs to the killer. Look at all three bodies — the wounds are essentially the same in shape and size, clearly made by the same tool. And all three victims wore short, curled hair. They wouldn’t have used hairpins.”

“If the hairpin didn’t belong to the victims, then it belongs to the killer. Does that mean the killer is a woman?” Bai Jin said it aloud and immediately looked uncertain. “Could a woman sever a human head? And with such professional technique?”

“An ordinary woman couldn’t. But a trained one could.” Shi Ting considered this for a moment. “We let our assumptions get the better of us from the start. The savagery of the scenes and the fact that there were three victims led us to take for granted that the killer must be male. By removing the heads, the killer may have been deliberately eliminating evidence of her gender to mislead us.”

E’Yuan said, “If it’s a woman, what would the motive be? Jealousy over the victims’ looks?”

“All three victims didn’t know one another. Was she planning to kill every woman more beautiful than herself?” Bai Jin dismissed E’Yuan’s theory.

“Whatever the motive, our time is running out. If we don’t crack the secret of these numbers right away, the next victim will appear very soon.” Shi Ting’s eyes darkened. “These numbers are almost certainly a murder announcement. The killer’s next target is probably hidden somewhere within this sequence.”

Though they now understood the killer’s intent, the three sequences of numbers remained as impenetrable as ever.

Back in Shi Ting’s office, Yan Qing saw that his desk was blanketed in photographs documenting each crime scene from every angle, capturing everything in its original state.

Shi Ting was convinced the killer had left some clue about the cipher key at the scene. He simply hadn’t found it yet.

“I’ll help you look.” Yan Qing pulled a chair to the opposite side of the desk and sat down.

Shi Ting looked at her and smiled softly. “Thank you, wife.”

“Oh — your Elder Sister is back. Mother and I went to visit her today.” Yan Qing picked up one of the photographs and mentioned it almost as an aside.

Shi Ting frowned slightly. “Why did she come back all of a sudden?”

“Apparently she had a quarrel with her husband. He took a concubine behind her back, and the concubine has already borne him a son.” Yan Qing gave a small shrug. “Men.”

“Your husband is also a man.” This particular comment clearly stung someone.

Yan Qing smiled. “I know my husband wouldn’t do such a thing.”

“So certain?”

“Have you forgotten what you promised me?” Yan Qing said, pursing her lips.

“I’ve forgotten!”

Yan Qing stared at him for a moment. She tossed the photograph she was holding across the desk at him. “Fine. I’m not helping you search anymore.”

The photograph landed in front of Shi Ting, and he glanced down at it instinctively. It was a close-up of the victim Boba’s dressing table — and the most eye-catching object was a square music box, its lid standing open.

“What are you looking at?” Yan Qing noticed he had gone quiet, his gaze fixed intently on one of the photographs, and looked over curiously.

“The dressing table is covered in cosmetics of every kind. Doesn’t it seem a bit out of place for a music box to be sitting there?”

“Perhaps someone had just given it to her and she was listening to it.” Yan Qing frowned a little at her own words. “But this music box is made of ordinary materials and the craftsmanship is rather rough. With Boba’s means, she wouldn’t have bought something this cheap herself. And if it had been a gift, the men who pursued her were wealthy or well-connected — they wouldn’t have sent something so inexpensive, and even if they had, she wouldn’t have accepted it, let alone actually listened to it.”

Shi Ting raised his sharp, bright eyes to meet hers, and something clicked between their gazes. “The music box may well have been brought there by the killer.”

He didn’t linger on the thought — he immediately sent someone to the scene. The music box was soon placed on his desk.

“Seventh Brother, I checked — there are no fingerprints anywhere on the music box.” Bai Jin also found it puzzling. “Whether it was a gift from someone or belonged to the victim, there’s no way it would be completely clean of prints. So your hunch is probably right. The killer brought it to the scene, and wiped away any fingerprints before leaving.”

“But why would the killer bring a music box to a murder? Did she want music playing while she killed?” Bai Jin pinched his chin. “That’s disturbing.”

Yan Qing was curious too. She put on a pair of gloves and gently wound the key at the bottom of the music box. Once it was fully wound, the box produced a delicate melody, and the pair of embracing figurines on top began to twirl and dance.

Yan Qing didn’t recognize the piece and couldn’t name it. But Shi Ting spoke up. “This is a very well-known piano piece. It’s called ‘The Swan.'”

“Could this be a clue the killer left for us?” Bai Jin thought for a moment. “The Swan is a foreign piece. The composer — what was his name again? Right — Losky.”

Shi Ting listened carefully to the melody drifting from the music box, his brow furrowing slightly. “If this is the cipher key, it wouldn’t appear only at Boba’s scene. Something similar should be present at the other two scenes as well.”

“I went over those scenes. Only Boba’s dressing table had a music box.”

When the music ended, Shi Ting immediately began sifting through the pile of photographs. No one was sure what he was looking for, and they all watched with curiosity.

“Found them.” Shi Ting pulled out two photographs, his eyes alive with excitement.

Yan Qing took them and looked. One showed a horn-shaped gramophone; the other showed a collection of musical instruments.

“Everything here is connected to music.” Yan Qing finally understood what Shi Ting had been searching for.

“Indeed.” Bai Jin set down the photographs. “The dance hall girl Xiu Xiu from Hongfan was killed at her own home, and she had a gramophone there. And A Ce from Dafa was killed in the dance hall’s rehearsal room, which was stocked with instruments for performance.”

Shi Ting rose. “Bai Jin, take some officers to the scene right now. Retrieve the record that was in the gramophone and find out the name of the piece A Ce was practicing to in the rehearsal room.”

“On it.” The new lead filled Bai Jin with renewed energy, and he left the office at a brisk pace.

Shi Ting tapped the desk lightly. “Now we need to find someone who knows music well.”

Yan Qing thought for a moment. “I actually have someone in mind.”

—