The seepage from the bottom of the anchor bay sounded like the phlegmatic chirping of a dying man, as if it were the final struggle for life. As Erin's tactical dagger pried open the last steel plate, rust slag fluttered into her collar as if it were a demonic taunt. The electronic lock on the dark door glowed with a cold, ghostly blue light, and the display was flashing three sets of numbers in a countdown -- the exact latitude and longitude coordinates of the first three victims at the time of their disappearance, as if counting down to their fate.
"We need the dead man's birthday." Erin's voice produced an eerie echo in the confined space, as if surrounded by countless ghosts. Leo's knuckles whitened as he held up the evidence bag, and the date of birth on the medical examiner's report showed signs of tampering under the ultraviolet light: Martha Clare's real birthday was three days earlier than the file recorded, a secret known only to her late obstetrician, as if it were a trap orchestrated by the killer.
By interviewing Martha Clare's former friends and family and investigating her social records, Erin discovers that she mentioned her special memory of her birthday in her diary, which leads to a clue to correcting the date of birth by entering a combination of corrected numbers.
As Irene entered the corrected number combination, the dark door suddenly spewed out cold mist mixed with the fishy odor of seaweed, as if opening the gates of hell. Leo's night vision caught the fleeting fluorescent graffiti on the wall -- it was a map of the Bay Area painted with radioactive paint, with each bridge seam marked with a time stamp of the disappearances. The most piercing red dot was landing at the coordinates of Erin's childhood bedroom, next to which was scrawled "Harper's Sacrifice," as if it were a provocation to her.
Family group photos pinned to the walls of the secret room swayed in the overcast wind, as if caressed by a ghost. Irene recognized one of them as a family photo from the night before her father's disappearance. There was an extra dark figure at the edge of the photo that shouldn't have been there, and when enlarged, it was visible that the man was missing the little finger on his left hand, and was holding up the Navy tag that now hung around Leo's neck, as if Leo was the key figure in the secret.
"Hydraulics activated!" The technician's scream came over the intercom with a hint of panic. Giant glass tanks behind the dark door were being filled with a pale green liquid, twelve unconscious victims were connected through rubber hoses to a central console, and the dashboard showed their vital signs being converted into binary code to be fed into the bridge stress system as if it were a wild experiment.
Erin's military boots crushed syringes all over the floor, and the residual mint-flavored solvent from one of them made her stomach convulse -- the exact same ingredient as the mints that Leo spent his days chewing on, as if it were Leo who was behind the tragedy. When she ripped away the canvas behind the console, rusty gear sets were driving the brass clock dials slowly, and a bloodied sapphire stud hung from the tip of the minute hand, the same one that had disappeared from her mother after her father's funeral, as if it were a cruel joke of fate.
"It's not Thomas's handiwork." Erin tweezed a strand of hair from a gap in the gears, and a quick DNA detector showed that it was Leo's hair. At that moment the hydraulic cages suddenly let out a deafening roar, and the control screen popped up with a warning that when the gears had completed twelve counterclockwise revolutions, all the victims would be poured alive into the main cable structure, as if a horrible catastrophe was about to befall them.
As Leo's sidearm pressed against Erin's backside, the minty flavor filled the bloody air as he whispered, "Your father was the first sacrifice." His other hand lifted the skin behind his left ear to reveal a microchip implanted under the skin -- the very same bridge stress monitor designed on Thomas' patent drawings three years ago, as if he were a participant in the plot.
As Irene touched the handcuffs around her waist, the room suddenly tilted 45 degrees, as if the world had turned upside down. Leo pulled the trigger at the moment of the fall, and the bullet grazed Irene's cheekbone, hitting the hydraulic hose, spraying solvents that corroded charred holes in Thomas's engineering log. A grease-stained blueprint fluttered down between the yellowed pages, labeled in her father's handwriting, "Abutment 122 Safe House." Erin instantly recalled that her father had inadvertently mentioned when she was a child that Bridge Abutment 122, due to its special geological structure, had been designed with an alternate safe space inside to house critical bridge maintenance information, which might be the key node in solving the entire mystery .
"You think I'm tracking down the killer?" Leo's sneer mingled with the clicking of gears biting together, "I've watched you search every crime scene for my father's severed finger since the day you transferred to Homicide." He suddenly ripped open his shirt, and nestled within the equilateral triangle tattooed on his chest was the Navy anchor chain motif -- the same tattoo as the one on the mysterious man in Thomas' treasured group photo, as if he were at the center of the conspiracy.
Erin knocked over the chemistry cabinet as she dodged the second bullet. The boiling mercuric nitrate solution snakes across the floor in bizarre trajectories that actually form a miniature model of the Bay Area Bridge. As the solution flowed through Leo's fallen peppermint candy wrapper, a sudden blue-green flame illuminated a hidden compartment in the ceiling -- where an old VCR was hidden, the tape labeled "Agent Harper's Disappearance Fact Book."
"The truth your mother didn't dare tell you." The metallic scrape of Leo pushing a bullet into the chamber was extraordinarily clear, "Back when the DEA was removing undercover agents, your father volunteered to be a bridge sacrifice..." His words were interrupted by the sudden activation of the video camera, the image of his father being tied up under a hydraulic press appeared in the snowflake screen, and Thomas, the young engineer standing in front of the joystick, was sticking a syringe into his neck -- the mint-colored solvent shaking in the syringe was exactly the same as Leo's pupils that were glowing with an eerie greenish light at the moment.
It turns out that Thomas was targeted by the drug cartel due to a financial crisis, and they threatened the lives of his family to force him to participate in this carefully planned crime, using his knowledge of bridge engineering to build a criminal layout. And Leo, under the threat of the drug lords, has been reduced step by step to an accomplice, responsible for the implementation of specific actions, including the laying of hands on Irene's father.
As the countdown entered the last ten seconds, Irene's hand that lunged for the console suddenly paused. The protective cover of the gear tachometer reflects the view behind it: Leo's shadow splits into two figures on the wall, one of which is raising a pistol with a silencer. The moment the trigger was pulled, Irene unscrewed the valve of the liquid nitrogen tank, and the splash of super-cold liquid solidified the bullet in mid-air, and Leo's right hand shattered into slush the moment it touched the white mist.
"The gears won't reverse." Irene embedded her father's pocket watch into the console notch, and the rusty clockwork suddenly began to tighten itself, "Because you're forgetting Thomas's true legacy--" A microfilm popped out from inside the watch, showing a surveillance screenshot of Leo's dealings with the drug lords in the anchor bay, dated the same day that Irene's father had disappeared.
By the time the SWAT team broke down the door, the hydraulics were back in safe mode. Leo's huddled, frosty torso suddenly convulsed, and the cyanide capsule hidden in his dentures rolled off with a sardonic grin, "You think you've won? When the twelfth main cable snapped..." His pupils deadened before spreading to Irene's right wrist, the five-centimeter scar bluing in the hypothermia -- the very wound caused by the distinctive serrations on Thomas's engineering knife.
The sirens of the emergency vehicles were heard as the technician found the encrypted diary at the bottom of the console. The latest entries show that Leo receives his commands via a subcutaneous chip, and the source of the signal comes from Alcatraz Prison across the bay -- where the mastermind of the bridge embezzlement twenty years ago, Erin's own uncle, whom Erin testified against in court, is being held. Erin then remembers that her uncle held a grudge against her father before he went to prison, and has been secretly plotting revenge ever since his release, using Thomas and Leo and others to accomplish his nefarious plans.