A food delivery man experiences bizarre swelling, creeping vision loss and stabbing pain around his eye, and doctors race to find the cause. Then, a woman is struck by bizarre symptoms that leave her on the verge of madness.

Doctors find that a baby's brain was infected in utero and take drastic measures to cure her. Then, a woman sees a dark shadow move across her eye and believes it's a worm, and a man is left with an unwanted Christmas surprise.

A 16-year-old boy near Seattle vomits his own fecal matter and doctors race to track down the killer in his insides. Then, mysterious rashes that ooze pus and blood spread across a teenager's body.

A young boy is plagued by a runny nose that quickly evolves into debilitating pain throughout his body. Then, a woman is driven to the brink of insanity by a deadly monster that's turning her body against itself.

A man vacationing in Belize breaks out in a rash of painful bumps and doctors struggle to uncover what is eating his flesh. Then, a teen develops a bump on her neck that causes debilitating weakness, dizziness and stabbing pains.

A family's cruise ship vacation turns into a living nightmare when their two year old swallows a sinister monster. Then, a mom is plagued with a mysterious infection and deadly parasites hijack the brain of a 6-year-old boy.

A high school football star contracts a mysterious infection that brings him to the brink of death. Then, a marina dock master suffers crippling pain in his left hand, and what's living inside is the stuff of science fiction.

A baby falls mysteriously ill and struggles to breathe, and doctors race to uncover the identity of the hidden assassin. Then, what starts out as mild groin discomfort for a globe-trotting man develops into paralyzing pain.

A toddler begins vomiting and convulsing and is pushed to the edge of death. Then, a neuro-psychiatrist suffers multi-organ failure and one of the deadliest infections on the planet causes legions across a woman's brain.

After getting a cut on his knee, a teen becomes feverish and fatigued, and the cause could result in amputation or death. Then, no one suspects something is destroying a young girl's retina.

When a teenage boy gradually stops breathing, doctors must bypass his lungs and oxygenate his blood. A personal trainer is afflicted by strange rashes and excruciating nerve pain.

A college student contracts something that eats her eyeball, causing headaches and severe light sensitivity. Then, doctors discover something insidious paralyzing a baby's body and threatening his life.

A baby nearly dies from something everyone has in their home. Then, a man has worms crawling throughout his lungs and a female boxer is blindsided by a rare infection.

A baby suddenly loses the ability to use the left side of her body, and doctors discover her brain was infected in utero. Then, a teacher's holidays are ruined by seizures that lead to brain surgery.

A teen develops rashes that leak pus and blood, and doctors discover he has one of the most feared diseases on the planet. Then, a tough ultra-marathoner is brought to his knees by a deadly infection that's shredding his organs.

Doctors discover a young boy drowning in his own mucus and on the brink of death is a victim of an infectious outbreak. Then, a mother fears her son has gangrene and takes matters into her own hands.

A horrendous creature infects the leg of a soccer coach and may lead to amputation and the end of his career. Then, a girl suffers from a brain infection that causes her to act out and threaten suicide.

In North Carolina, a young couple both start experiencing a deluge of bizarre and terrifying symptoms and the origin of their infections is startling. In Texas, a local councilman experiences strange cravings and baffling weight loss at the hands of a hidden enemy that attacks his blood and organs. In Maryland, a young boy endures extreme nerve pain and rashes across his body. His parents can only lament as the mysterious illness takes him to the edge of death.

Doctors discover a teenager's brain is under attack when she suffers seizures and blindness, and a young child develops a rash and fever that won't go away.

A young man with a toothache ends up fighting an infection that threatens to eat him alive. Then, a young boy wastes away in front of his parents' eyes as a mysterious infection overtakes his body.

A teenager's shoulder pain leads to her being quarantined and facing the possibility of losing her life. Then, a woman struggles through her work week as something causes her body to rot.

A war veteran that fought in Afghanistan is taken down by an even more mysterious enemy. Then, new parents are horrified when a deadly infection pushes their baby daughter to the brink of death.

A common sore throat spirals out of control and a teenage girl is left clinging to life. Then, what a world traveler takes for a simple skin irritation turns out to be something far more menacing.

A contractor suffers a bump on his head and finds himself in the ICU fighting for his life. Then, doctors discover the threat behind a college football player's blinding headaches could easily end his life.

A man emerges from surgery just in time for Christmas but soon finds himself on the brink of death. Then, a woman is out Christmas shopping when a stabbing pain in her eye is so severe, she believes she sees shadows of worms.