Blood dripped from his lips and coated his skin in a sickly red.

He grinned, his teeth stained red.

His eyes flashing with hunger.

Despite already being fed.

Licking his blood-coated lips, he blinked in the darkness. The silence was only broken by his laboured breaths and the dripping of a pipe. Adrenaline coursed through his veins; sparks of electricity. He looked down at the body at his feet and grinned.

The thrill of the kill was still fresh

As fresh as the blood on his lips…

Growling, he scrunched the torn, orange mask in his fist and stepped over the body, heading out into the night.

Searching for another kill.

"Man, Leo's been acting weird ever since we got back," Mikey said, glancing over his shoulder towards his eldest brother.

Leo knelt in front of the blank TV, hands curled into fists as he stared blankly at the black screen.

"He's been through a lot, Mikey," Don said, also looking at his eldest brother. "I've given him an antidote for the poison, but his body's still in shock."

"Why's he doing that?" Raph asked, nodding in Leo's direction. "Just starin' at nothing?"

"I'm not sure," Don admitted. "I think it's just his body trying to adjust to the effects of the antidote. He should be feeling better in the morning."

"If I ever catch those Foot scum…" Raphael growled angrily.

"What even was that stuff?" Mikey asked.

"I'm not sure. I haven't seen anything like that before."

"Are you sure he'll get better?"

"My test results showed that the antidote should get rid of all of the poison in his system. Trust me, he'll be better by morning."

Later that night, Don entered his lab, ready for bed. He quickly checked to make sure he had saved all the files on his computer- he wasn't sure if Mikey had been playing around with his stuff again. He stopped when he reached his work station. Bending down to peer into the microscope, Don looked back over Leo's blood sample.

His blood ran cold.

His heart stopped beating.

"Oh no…"

A door creaked on rusted hinges.

Raphael groaned and rolled over in his bed. "Leave me alone," he grumbled, still half asleep.

Footsteps sounded on the floor, approaching his bed.

"Leo, what are you doing up?" Raphael asked, rubbing his eyes as he sat up in bed. "How ya' feeling?"

No response.

"Leo? You ok bro?"

Footsteps.

"Leo, what are you doing?"

Silence. A flash of a smile.

"Leo…Leo don't, you're sick. Leo, please, stop!"

The smell of blood was heavy in the air.

Leo grinned.

Raphael screamed.

One more to go, Leo thought, surveying the city below him.

He could smell him. He was close.

Leo grinned and gripped his blood-stained katannas.

"You can run little brother, but you can't hide."

Unknown to Leo, a shadow on the next rooftop observed him silently. The shadow smiled and held up a small device.

"The toxin works. He's hunting down the last one as we speak."

"Excellent."

"What do you want me to do with him when his mission is complete?"

"Simple. Kill him."