Monsters can hijack our bodies in any number of ways. A man breaks out in a mysterious painful rash. A woman experiences bouts of piercing pain in her throat. A teen girl is left debilitated by strange spells of dizziness and fatigue.

Three families are turned upside down by deadly monsters. A 4-year-old boy is plagued by crippling pain. A college student with a small cut ends up fighting for her life. A woman is driven to insanity by an intruder in her own body.

Three infectious diseases ruin the holidays. A Christmas baby is born, but her brain was infected in utero. A woman sees a dark shadow move across her eye & believes it's a worm, & a man is left with an unwanted Christmas surprise.

A young girl is brought to the hospital with stabbing pains in her scalp. A wife and mother is struck down by a severe string of mysterious symptoms. A deadly invader turns a relaxing vacation into a nightmare.

A man falls comatose. A college student's sore throat turns deadly. A woman's bizarre symptoms confound experts.

A man experiences bizarre swelling around his eye. A 12-year-old girl falls mysteriously ill. A young woman is struck by a bizarre set of symptoms that leaves her on the verge of madness, and no one can understand why.

An infant falls mysteriously ill. A biology professor becomes an unexpected host. A family man is brought to the brink, all in this episode of Monsters Inside Me.

A woman who has recently given birth is in critical condition. A young boy has signs of a mysterious infection that no antibiotics can cure. A young man feels excruciating pain and doctors discover something has invaded his brain.

A boy is struck down with a strange condition. A woman has bizarre symptoms that push her to the brink of madness. A toddler falls into a trance-like state.

A teenager develops mysterious blotchy sores. A tough athlete is struck down by a rare disease. 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 paralyzed. A young father grapples with a monster that threatens to blind him. A woman's excruciating pain confounds experts.

A young woman is struck down by a dangerous parasite. An infant becomes mysteriously ill. A Midwestern man is brought to the brink by a deadly fungus.

Three unwanted Christmas surprises. A man bangs his head and is left fighting a one-in-a-million medical mystery. A wound in a boy's knee harbors an uninvited guest. And a man unwittingly feeds his own intended killer.

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.

Dr. Jeff Young & his crack team treat and save the lives of countless pets at one of the busiest clinics in America. In this episode, Jeff is faced with saving a dog that goes into cardiac arrest shortly after arriving at his clinic.