Three women living in vastly different locales have one thing in common: they've become unwitting hosts to baffling and deadly terrors inside them.

When three unsuspecting young families are thrown into a tailspin, they are shocked to learn of the tiny culprits wreaking havoc on their lives.

A Massachusetts EMT is shattered by a routine emergency call when she discovers that the victim is her son, and a tough guy is brought to his knees.

A contractor suffers a bump on his head while he is working, but days later, he finds himself in the ICU fighting for his life with something in his brain.

What begins as a common sore throat quickly spirals out of control for a teenage girl, as a rare affliction leaves her clinging to life.

In Tennessee, new parents are horrified when a deadly infection pushes their baby daughter to the brink of death. Can she be pulled back by doctors?

Trouble is lurking in the bodies of three different women. In rural Washington State, a teenager's shoulder pain leads to her to quarantine in a matter of days.

Three healthy people with a love of the outdoors are struck down by a menace that lurks inside them. In Ohio, a young boy wastes away in front of his parents.

Three lively people suddenly come face to face with their own mortality. In Virginia, a teen suffers seizures and sudden blindness when her brain is attacked.

The lives of three families are turned upside down, a couples' dream home is a living nightmare, and an insidious creature takes a man's spleen.

The lives of three families are jolted - one infection rips a man's leg apart, and a rare brain infection pushes a seven year old girl toward suicide.

A mysterious outbreak leads to a four year old boy drowning in his own mucus, and a wound in a seven year old's knee has a vile cause.

A mysterious infection brings a tough athlete to his knees, a teenager contracts a feared disease, and a woman's brain is practically set on fire.

A Christmas baby is infected in utero, Hanukkah is upturned by an infection, and a school teacher's Thanksgiving is disrupted.

A baby nearly dies at home, a man has worms crawling throughout his lungs, and a female boxer gets blindsided by a rare infection.

An infection may rob a college student of her eyeball, a mysterious infection paralyzes six-month old boy and a mother endures horror after birth.

One affliction shuts down a teen’s lungs, another attacks the nervous system of a personal trainer, and a third infection eats the blood of a health worker.

One eats the leg of a teenage boy, another afflicts a couple, and tears their lives apart. And insidious worms hijack an eight year-old girl's eyeball.

A baby girl writhes in pain on the verge of death, a neuro-psychiatrist suffers multi-organ failure, and a woman suffers a baffling brain infection.

A man experiences bizarre swelling around his eye. A 12-year-old girl falls mysteriously ill and a young woman's symptoms leave her close to madness.

A young girl goes to hospital with stabbing pains in her scalp. A woman is struck by severe, strange symptoms that threaten to tear her family apart.

A woman who recently gave birth is in a critical condition. A young man feels excruciating pain and doctors discover something has invaded his brain.

A boy is struck with a serious fever. A woman has bizarre symptoms that push her to the brink of madness, and a toddler falls into a trance-like state.

A man falls comatose. A student's sore throat turns deadly, and the monster destroying him is shockingly common. A woman's bizarre symptoms stun experts.

A teenager develops mysterious blotchy sores. A tough athlete is hit by a rare disease that make him hallucinate. Plus, a woman battles strange bouts of vomiting.

A man starts coughing up blood. A newlywed husband is struck down by a rare disease. A young father experiences crippling abdominal pain.

An infant is suddenly paralysed. A young father grapples with a monster that threatens to blind him. Plus, a woman's excruciating pain confounds experts.

A man bangs his head and fights a rare medical mystery. A wound in a boy's knee hosts an uninvited guest, and a man unwittingly feeds his own killer.

A young woman is struck with a dangerous parasite covering her in oozing sores, whilst a man is brought to the brink by a deadly fungus.

A man develops a strange growth on his wrist. A nurse sees twig-like pieces in her urine. A pregnant woman falls dangerously ill with flu-like symptoms.

In Colorado, a woman's health spirals out of control when 'the flu' turns out to be far more serious. Explore this and other cases of flesh-eating monsters.

In North Carolina, debilitating pain and nausea haunt a mother for more than four years. When doctors finally find the culprit, it sends everyone reeling.

In Illinois, a newly engaged man mysteriously collapses and faces organ failure. His fianc? gazes in horror as he must choose between life and limb.

In Texas, a ballerina descends into a downward spiral of debilitating migraines and muscle failures. What is sapping the life out of this once vibrant girl?

In Alaska, an enigmatic condition leading to bizarre hallucinations hits a burly oilrig worker. What could possibly be taking down this tough guy?

A young woman is on a trip in Burkina Faso when she suddenly suffers from excruciating bouts of nausea and diarrhoea. Can she find medical help before it's too late?

A teenager who is recovering from a trauma wound suddenly suffers from a life-threatening infection. Can his doctors help him before his body shuts down?

This show retells the real-life, harrowing dramas of people infected by deadly parasites as doctors and scientists try to unravel each case before it's too late.

Three victims each receive a monstrous Christmas present, including a woman who feels a stabbing pain in her eye and apparently sees worm's shadows.

A baby falls mysteriously ill and struggles to breathe. A man has something living in an embarrassing place. Plus a woman's weight gain confounds experts.

A mysterious infection brings a football player to his knees, parasites devour a woman's eyeball and sea creatures attack a marina dock master!

A family's cruise ship holiday becomes a nightmare when their toddler swallows a sinister monster. Plus, a mother of two is plagued with a mysterious infection.

A man breaks out in a mysterious painful rash. A woman suffers bouts of piercing pain in her throat, and a teen is hit by unexplained dizziness and fatigue.

A four-year-old boy has crippling pain, a student with a small cut verges on death, and a woman is driven to insanity by a monster in her own body.

A boy vomits his own fecal matter and a teenager contracts one of the most feared diseases on the planet. What monsters are hiding in the backyard?

An infant suffers terrifying seizures. A biology professor in a strange experiment becomes an unexpected host. A family man is hit by thousands of parasites.