Song Sheng

Biodata

Background / History

Adoption and Early Life

Song Sheng was adopted by the Song family when she was just over a month old. Less than a year later, her adoptive parents had a biological daughter, Song Xiao. Their attention to Song Sheng diminished after Song Xiao’s birth; by high school, she was earning her own tuition 20 22.

She studied chemical engineering and later worked at a metal-smelting factory. The factory owner regarded her as intelligent and hardworking 23 24.

Relationship with Zhang Zhao

About a year before the case, Song Sheng met Zhang Zhao online. They began dating after approximately a month of conversation and an in-person meeting. He subsequently became abusive, hitting and insulting her when drunk, then begging for forgiveness once sober. Her softheartedness made it difficult for her to leave him 22.

Zhang Zhao also harassed her at work. Song Sheng transferred from marketing to behind-the-scenes work because the factory laboratory’s entry restrictions kept him out, but he continued waiting for her at the gate 24.

After an argument, they went more than a month without seeing each other. When Zhang Zhao eventually demanded that they reconcile, Song Sheng refused 22.

Attack on the Song Household

Zhang Zhao knocked Song Sheng unconscious, stole her keys, and went to her family’s home, blaming them for their separation. After regaining consciousness, she called Song Xiao to warn her and hurried home. She confronted Zhang Zhao and insisted that leaving him had been her own decision, not her family’s 22.

Song Sheng said she had called the police on the way. Zhang Zhao initially pretended to leave, then seized her and released mercury vapor into the bathroom where her family was confined. He prevented her from rescuing them until Song Xiao freed herself and struck him from behind 23.

The sisters moved Zhang Zhao into the bathroom, but he regained consciousness. Song Xiao injected him with a powerful sedative and repeatedly slammed him against something until he stopped breathing. Their parents, driven into hallucinations and self-injury by mercury poisoning, also died 30.

Cover-up and Identity Exchange

Song Sheng comforted her distraught sister and devised a plan to take responsibility. She proposed disguising the deaths as mercury-poisoning suicides and remaining at the scene long enough to become mentally confused without dying. Song Xiao was to hide at the factory and dispose of the stolen mercury vapor 30.

When Song Xiao feared that her sister would be executed, Song Sheng revealed that she was pregnant and promised that she would not die. She later returned with blood covering her face and asked Song Xiao to give her another painkiller injection 30.

The sisters exchanged identities. The real Song Sheng entered the hospital as “Song Xiao,” her disfigured face concealed by bandages. The real Song Xiao posed as “Song Sheng,” wearing a mask. Their similar ages and builds, along with the same broad blood type, helped sustain the deception 29.

Exposure of the Deception

While hospitalized under her sister’s name, Song Sheng gave investigators a misleading account that concealed the identity exchange and her cover-up. She eventually claimed responsibility for Zhang Zhao’s death but refused to explain the details 22 23 27 28.

Meanwhile, the masked woman pursued at the factory and captured after attacking Pei Qingyu and Xun Yin was Song Xiao, not Song Sheng. The narration and investigators initially used the assumed identity 25 26 27 29.

A hemolytic reaction during Song Sheng’s transfusion exposed a medical inconsistency. Pei Qingyu and Xun Yin established that the sisters had different blood subtypes and contraindications despite sharing the same broad blood type. Pei Qingyu then confronted Song Xiao with the identity exchange, prompting her account of the killing and Song Sheng’s plan 28 29 30.

Missing Evidence and Listening Devices

When questioned directly, Song Sheng initially refused to disclose the location of the two syringes. She said she had wiped Song Xiao’s fingerprints from the knife and left her own, arguing that the police lacked physical evidence against her sister 31.

Pei Qingyu challenged her attempt to evade accountability and appealed to her concern for her unborn child. Song Sheng finally admitted that she had detached the needles and hidden them between the sofa cushions. Wang Yu found needle holes but discovered that someone had already removed the evidence 31 32.

Listening devices were subsequently found on both sisters. Song Sheng reported that a stranger at the factory had supplied them, claiming the devices would save their lives. She later identified that person as Zhuo Wumian. The syringes were recovered, and Xun Yin arranged for their delivery so Song Ranran could close the case, with the Zhuo Wumian evidence handled separately 44.

Appearance

• Similar build to Song Xiao: Their physical resemblance in age and build helped make the identity exchange plausible 29.
• Facial disfigurement: Her injured face is extensively bandaged during her hospitalization, concealing her identity 22 29.
• Lasting sensitivity: Song Sheng says that, since being disfigured, she has become especially alert to unfamiliar people approaching her 32.

Personality

Song Sheng is described as gentle, softhearted, timid, and insecure. Pei Qingyu connects her intense need for close relationships to the neglect she experienced in childhood. These vulnerabilities contributed to her difficulty leaving Zhang Zhao despite his abuse 22 32.

Her fear does not prevent her from resisting him. She refuses reconciliation, warns her sister about the danger, and confronts him over imprisoning her family 22 23.

Her protectiveness toward Song Xiao becomes self-destructive: she accepts dangerous mercury exposure, conceals evidence, and attempts to assume responsibility for a killing she did not commit. Despite her distress, she can plan methodically and challenge investigators over weaknesses in their physical evidence 30 31.

Abilities & Skills

Chemical-Engineering Knowledge

Song Sheng studied chemical engineering and worked in a metal-smelting factory 23 24.

• Uses her understanding of mercury poisoning to plan a staged scene and controlled exposure 30.
• Directs Song Xiao to dispose of mercury vapor stolen from the factory 30.
• Her own exposure causes severe pain and poisoning; her knowledge does not protect her from its effects 30.

Evidence Concealment and Deception

Song Sheng organizes the cover-up intended to protect her sister 29 30 31.

• Exchanges identities with Song Xiao and maintains the deception during hospital questioning 22 23 29.
• Removes Song Xiao’s fingerprints from the knife and leaves her own 31.
• Conceals the detached syringe needles between sofa cushions 32.
• Fails to account for the sisters’ differing blood subtypes and medical contraindications, which expose the identity exchange 29.

Relationships

• Song Xiao — Younger adoptive sister and the person Song Sheng attempts to protect by taking responsibility for Zhang Zhao’s death. Their identity exchange is central to the cover-up 20 29 30.
• Adoptive parents — Adopted Song Sheng in infancy but largely neglected her after Song Xiao’s birth. Both die following Zhang Zhao’s mercury attack 20 22 30.
• Zhang Zhao — Abusive former boyfriend. His refusal to accept their separation leads to the attack on her family 22 23.
• Pei Qingyu — Investigator who exposes the identity exchange and persuades her to reveal where she hid the needles by confronting the consequences for her unborn child 29 31 32.
• Xun Yin — Investigator who helps verify the sisters’ identities and directly questions Song Sheng about the missing syringes 29 31.
• Zhuo Wumian — Supplies the listening devices carried by the sisters under the claim that they will save their lives; Song Sheng later identifies him 44.
• Factory owner — Employer who praises her intelligence and work ethic and describes Zhang Zhao’s harassment to investigators 24.

Notable Quotes

“They didn't stop me. I'm the one who doesn't want to be with you anymore.” 22

“Be good. You weren't the one who killed him. It was my fault. If it weren't for me... none of this would have happened. I've wanted to kill him for a long time.” 30