Olivia and Sherlock were just approaching a set of steel stairs leading to the second floor of the warehouse when Sherlock halted, his head turning slightly. Realizing that the detective had heard something and knowing better than to ask what he'd heard, Olivia turned to look at him. Sherlock's eyes swept the dark room as the beams from their flashlights bounced off the walls, illuminating the shadows. Olivia didn't know what he'd heard, but she trusted his instincts. Her own senses were tingling.

A black shape suddenly hurtled from the shadows and knocked Sherlock to the ground. Olivia was turning to confront it when something else rammed into her torso. She fell against the ground, half-winded, and instinctively kicked out. Whoever - whatever - was on her grunted and reeled backwards as her foot made contact, and then Olivia was pulling out her gun and firing three shots into the black mass on top of her. It instantly went limp and fell to the side, half-on top of her. The agent scrambled to her feet and grabbed her flashlight where she'd dropped it on the ground. Swinging it around, she saw that her attacker had been a man in his mid-30's, Caucasian, with short dark brown hair and nondescript clothes. He lay on the ground, dead.

Sherlock.

Olivia was whirling around to help the detective when a shot rang out, echoing in the vast space and landing a foot away from her. As soon as she heard the sound, the woman turned and fired in the direction the bullet had come from. She heard a yell of pain, then the sound of running footsteps. Someone standing on the second level, near the stairs, was on the move. She'd hit him, but not fatally. As shots rang out again, aimed towards her, Olivia ran for cover. Ducking behind a pillar, she glanced around.

Sherlock was in the midst of wrestling with another attacker, who looked similar to Olivia's assailant. The attacker had pinned Sherlock to the ground, but the detective was putting up a fight. As the Englishman twisted to swing his right fist as his assailant's jaw, the gleam from Olivia's flashlight caught on something bright in the inside of Sherlock's jacket. It shone for a moment in the light, and Olivia's heart stopped as she realized what it was.

He had the antidote.

Walter must have finished it while Olivia, Peter, and John were away, and Sherlock must have taken it with him for whatever reason. Olivia knew Walter had been making only a small amount because of the high concentration, enough to fit into a small glass vial. If they lost the one Sherlock had with him, it would take too long for Walter to make more. Lives would be lost.

The horrifying idea was registering in Olivia's mind when Sherlock's attacker slammed his fist into the detective's face, knocking his head backwards onto the cement ground and stunning him momentarily. The man wasted no time in searching Sherlock's pockets. He was there for the antidote. And - judging by the way the person on the second floor was now covering him by firing some warning shots in Olivia's direction - all three of the attackers were there for the antidote. Sherlock looked like he was slowly refocusing again, but his attacker had already found the glass vial. The man picked himself up and off of Sherlock, then pulled out a gun and aimed it at the still-dazed detective.

Olivia threw all caution to the winds.

"HEY!"

With a yell, the agent threw herself from the safety of the pillars. With her left hand, she aimed the beam of her flashlight towards Sherlock's attacker. With her right hand, she sent three quick shots in the direction of the gunman on the second floor as her eyes picked him out of the darkness. Judging from the sound of a body falling, she'd hit her mark. At her yell, the man attacking Sherlock looked over, and was momentarily blinded by the light. He took a staggering step backwards, then recovered enough to see Olivia's gun aimed at him.

Olivia had expected him to give up. She had expected to him to surrender, or try escaping, or even fighting back. She did not expect him to throw the vial into the air. The man obviously hadn't realized that his partner on the second floor was dead.

Glass vial clutched in his hand, the man drew back his arm to throw it up to the second floor. Clearly, he hoped that if he couldn't escape with the antidote, his friend could. At that moment, Sherlock - who had fully regained focus - hooked one of his long legs around the attacker's, and yanked him off balance. Unfortunately, the man was already in the process of throwing the vial.

"NO!"

Dimly, Olivia knew that Sherlock had dragged his assailant to the ground and subdued him, but her attention was focused on the antidote. The glass vial flew up into the air haphazardly, its surface once again shining - almost mockingly - in the beam from Olivia's flashlight. Then it began to fall. If it hit the cement ground, it would surely shatter.

Olivia sprinted towards it, gun and flashlight forgotten, and threw herself forwards. Everything around her dimmed as her eyes locked on the glass vial, focusing on the trajectory of the fall. She could make it. She had to. Time seemed to slow down, as did the glass vial's descent. Olivia hit the unforgiving ground, hand outstretched, already imagining the sound of breaking glass.

But it didn't come. As the detective watched in disbelief, the antidote slowly descended, as if on a cushion of air, and came to rest on the ground just a few inches beyond Olivia's hand. It landed on the cement with a quiet clink - fully intact.

There was the sound of footsteps, and Sherlock appeared next to Olivia, who slowly got to her feet and picked up the vial. As she stared at it in her hand, thoughts flying through her mind, the detective raised his eyebrows.

"Agent Dunham, you've been holding back a key piece of information. The Cortexiphan trials in Wooster, Ohio weren't the only ones, were they?"