At 4:12 on a rainy Tuesday afternoon, Rachel Carter brought her eight-year-old son into the emergency department at St. Matthew’s Hospital.

In the dimly lit sub-basement laboratory beneath St. Matthew’s Hospital, Dr. Lena Brooks was working at a furious pace under the yellow light of an old halogen desk lamp.

Eli lay on a stainless steel examination table, breathing shallowly through a portable oxygen mask. Marcus sat beside him, holding a bag of saline high above his head while manually pumping a pressure cuff to keep the boy’s blood pressure from collapsing.

"His oxygen saturation is down to 82%," Marcus warned, his voice tight. "Lena, we're running out of time. His heart is going into arrhythmia."

"I'm working as fast as I can!" Lena shouted, her hands shaking as she calibrated an old centrifugation machine. "The vial Eli brought contains the active synthetic toxin, but without the specific neutralizing immunoglobulins, any blood transfusion we give him will just cause another massive hemolytic reaction!"

The heavy steel door of the basement lab suddenly banged open.

Marcus reached for a heavy iron pipe resting against the wall, preparing to swing, but stopped when Detective Ramirez stumbled inside.

She was covered in mud and blood, supporting a half-conscious Katherine Vance, whose coat was soaked in crimson.

"Get her on the table!" Ramirez gasped, helping Katherine collapse onto the adjacent medical gurney. "State police secured the bridge. Julian Thorne is in custody, but she’s lost over two liters of blood from a gunshot wound to her flank!"

"Mom!" Eli squeaked through his oxygen mask, trying to sit up.

"Eli..." Katherine whispered, her eyes fluttering open as she heard her son’s voice. She reached out her pale, trembling arm toward him. "My baby... my sweet boy..."

"Don't move, Katherine," Lena commanded, rushing over with a large draw-needle and sterile collection bags. "You have the antibodies in your plasma, don't you?"

"Yes..." Katherine rasped, wincing in agony as Lena found a viable vein in her forearm. "Type O-negative... same as Eli. Take... take whatever he needs. Don't worry about me."

"You're bleeding out internally," Lena said, her professional instinct warring with the desperate urgency of the situation. "If I draw a full unit of blood from you right now in your condition, your heart could stop."