He'd ignored the buzzing of his cell in his pant pocket, figuring it was Beckett texting him back.
In trained precision, he'd scoped out the guest bedroom and bath, his index finger gently curled around the trigger of his Glock as he moved through the apartment, carefully setting one foot in front of the other, walking on rice paper.
The adrenaline fueled his body, setting all his senses on high alert as he headed toward the large kitchen, noting the lingering smell of reheated lunch.
A dull thud made him tense up, the bone chilling noise followed by the sound of a gun sliding across the old hardwood floors.
Kevin.
His heart knew it before his eyes had a chance to find the young detective's still form on the ground, arms splayed out to either side, eerily unmoving.
Muttering a silent curse under his breath, Esposito slowly approached the area, sensing, rather than seeing their killer.
The large kitchen island was the centerpiece in the otherwise barren room, holding boxes of packaged noodles and newspapers. In his tension-filled state, he almost missed a small, dried blood stain on the front of yesterday's Times.
Taking one more cautious step, Esposito approached his partner to check for any signs of breathing.
There was a good chance that leaving Kevin's body there was a trap. Or perhaps, the young detective had gotten too close to the killer and had to be neutralized before flight was possible. But Esposito hadn't heard any steps near the front door, the very spot he'd particularly kept an eye on after they split up.
Glancing around one last time and not seeing any signs of a threat, he moved closer to his partner, his feet barely leaving the floor as he inched his way along.
By the time he was practically on top of him, everything remained still. The scent of fresh blood grew stronger as he approached that general direction, leaving him to guess that their victim would be found in the master bedroom.
A silent prayer stayed on the tip of his tongue as he went down on one knee, swiftly reaching for the side of his partner's neck.
Much to his relief, his index and middle finger detected a strong pulse, followed by a soft exhale he felt on the top of his hand.
Years of combat-built intuition made him stand back up immediately, doing so in time to hear rattling dishes on the counter and papers to falling to the ground.
Instinctively dodging to the left, Esposito saw Danny out of the corner of his eye, moving faster than he'd ever seen any human being move, skillfully navigating the kitchen island before jumping to the ground and charging after him.
His expression was a grotesque mask of mixed emotions from hysteria to blood lust, the corners of his mouth crusty from saliva running out of them. There was a cut on his right cheek bone, likely inflicted by his last victim.
With a shriek, Danny ran toward him, the knife drawn, his slim body zig-zagging to make for a difficult target.
Esposito spun around his axis, trying to get in a good shot when he lost sight of him altogether.
For a terrifying fraction of a second, he scanned the room top to bottom, unable to make out anyone but Kevin. In a moment of despair, he even resorted to checking the ceiling, not finding their suspect there either.
The next thing he heard was the swoosh of air from somebody moving behind his back. With hardly enough time to react, he dodged to the left once more, narrowly missing the sharp edge of the knife that had been intended to slash his throat.
Instead, it pierced the fabric shoulder strap of his tactical vest before entering his back, the pain intense enough that he lost his grasp on the Glock, the gun dropping to the floor.
As though he was unhappy that his attack hadn't yielded a killing wound, Danny shrieked again, jerking on the knife's handle when it didn't give right away.
The agony of the blade being pulled out of the wound caused Esposito to go down, the world turning to a frenzied circus of pulsating bright lights.
His instincts told him to roll off to the side, create distance between himself and the unscrupulous attacker. Yet, upon attempting it, his right arm gave out, causing him to remain on his back, a vulnerable target for his attacker.
Breathing heavy, he tried to get up on the left but failed when Danny jumped on top of his chest, his wide eyes filled with glee as he raised the metal blade to his mouth and licked the fresh blood.
"I taste fear…", he rejoiced before reaching down to run a hand through Esposito's wavy black hair, "Don't worry. It's almost over."
It wouldn't be over, at least not as long as there was a breath left in him, the detective swore and moved his good hand down the length of his BDU's, part of them covered by the other man's thigh.
The secondary handgun secured along his ankle was too far out of reach, but his knife wasn't.
Just as Danny was setting up to cut his throat, he loosened the clasp holding it in place and rammed it into the killer's side, the thrust enough to slow his movements but not stop him completely.
The bloody knife was still coming for his throat, even though there was surprise and terror replacing the cold determination in Danny's eyes.
With one hand tied up and the other barely functioning, Esposito pushed his feet against the floor for traction, then rolled off to the side, throwing his assailant off balance completely.
With the injury beginning to take its toll, Danny was slow to gather his bearings, muttering something under his breath that Esposito couldn't understand beneath the throbbing in his ears.
Lying on his good side, he scanned the floor for his gun, seeing the barrel sticking out around the corner of the kitchen island, still too far from reach.
Surprisingly, Danny showed no interest to go for it and finish a sloppy job in the making. Instead, he pressed a hand onto his side, careful not to move the knife still in the wound, and crawled back to his feet, his eyes filled with confusion and anger.
"You are…bad…you all are…bad…", the young man growled, swaying dangerously as he got up, then staggered off without another word.
As the adrenalin in his body began to wane, Esposito dropped his head to the ground, trying to preserve energy as he reached around his chest for the phone in the right pant pocket.
He had to tell Beckett.
Now.
Ignoring the coppery smell and streaks of his own blood that were smeared across the floor, he retrieved the phone, taking a moment longer to pull up her number and hit the button.
"Beckett?", he heard her worried voice on the other end, and swallowed the nausea.
"He's running out of the apartment. He's hurt but…fleeing. Got him with my…knife."
"Espo, are you guys ok?"
The terror was seeping through each of her words and he glanced off to the left where his partner was still lying on the floor, unmoving.
"Not good…but ok.", he sighed and exhaled slowly, trying to keep his heart rate under control, "Go get this son of a bitch."
"Will do. I'll have Castle call in an ambulance. Hang in there, guys."
When he heard the click on the other line, Esposito dropped the phone back down, the agony so unbearable that it threatened to drag him into the oblivion of unconsciousness.
But he couldn't quit now.
Instead, he immobilized the last of his reserves and rolled over his injured shoulder to lie on his stomach, the sheer movement rewarded with a searing pain that enveloped his chest for many long moments.
With the cold sweat running down either side of his face and dripping onto the slippery floor, he let out an involuntary groan, the raspy wheezing coming out of his dry throat only adding to his misery.
"K'vin.", he croaked and inched his way closer to his still partner, "C'mon bro. You gotta…wake up. Cause I don't know how much longer I can stay awake."
When he was close enough that his bloodied hand could reach the back of his partner's head, Esposito went down again, giving his body a small reprieve while carefully tugging on a few loose strands of Kevin's hair.
When that didn't work, he resorted to flicking him with his middle finger, the motion enough roust the young detective, but not fully come back too.
It didn't matter, he tried to reassure himself, Beckett would have Castle call in support and this would be over with soon. Or would it?
When he felt the darkness encapsulate him, Esposito sighed quietly, his mind travelling to Allison who would be safe on the West Coast, completely oblivious to the current situation. Then it wandered to his team and the lengths they'd gone through to catch Danny. Then his partner and best friend, of course.
Using the last of his energy, the grasped the back of Kevin's neck tightly, and closed his eyes in silent defeat.