These are the cases of law enforcement officers facing monsters no training could ever prepare them for.
From training grounds to war-torn battlefields, a growing number of soldiers report encounters not with enemy combatants - but with something beyond the known world.
These are the chilling encounters of people who trespassed into the domain of the unexplained and paid the price.
These are the chilling accounts of people who claim they were hunted by mysterious cryptids; from a Dogman in Ohio, a group of Bigfoot in Washington state, a Skunk Ape in Florida and a mysterious Wendigo in Wisconsin.
An expedition tries to tag the first great white shark in the Atlantic; divers attach a camera to a great white shark to study why they are becoming more aggressive predators.
Giant pythons have been discovered in parts of Florida for more than a century, but their territory has spread rapidly since 1992's Hurricane Andrew, prompting the team to investigate whether the snakes could threaten the rest of the United States.
Examining how giant killer bees from South America are spreading northward into the United States, attack with ferocity and might be adapting to colder temperatures, which would make them an even greater threat.
Investigating sightings of a giant winged monster known as "Mothman" across America; the monster is blamed for terrorizing a town in West Virginia where a bridge collapse claimed 46 lives in 1967.
Investigating whether South American piranhas appearing in U.S. lakes and rivers are adapting, can breed and cause devastation.
A humanlike beast with reptilian skin, reportedly, has been terrorizing Flatwoods, W.Va., since it was first sighted in 1952 hovering over its victims in a strange craft and emitting noxious gases.
The team investigates reports of aggressive and territorial packs of sasquatches in the Sierra Nevada Mountains of California; examining footprints and new video.
The team heads into Midwestern forests to investigate werewolf sightings; recently uncovered film footage and new witnesses.
Inventor Robert Rines, who believes he saw the Loch Ness Monster surface in 1972, searches for evidence to prove his theory that the creature has died.
Investigating whether the slayings of hundreds of cattle every year in the United States are related to cult activity, predators such as wolves, or a creature that has not been identified yet.
A swamp beast immortalized in the film "The Legend of Boggy Creek" is said to stalk the residents of a small town in Arkansas; two teams search for evidence of the swamp monster's existence.
A team seeks out the truth behind 250 years of stories about the Jersey Devil, which has been described as a winged half-bird, half-horse creature with hooves, a reptilian tail and a scream that echoes through New Jersey's Pine Barrens.
An urban legend comes true during the 1930s when New York City workers find swarms of alligators living beneath the busy streets of the metropolis; modern herpetologists and explorers search for alligators in the sewers of New York City.
Tales of a large hairy creature that preys on elk and frightens people have echoed through the Colorado Rockies for centuries; a team scales Pikes Peak to hunt for the legendary beast.
Investigating sightings of a 60-foot shark that might be a giant new species or a prehistoric survivor in the waters off Mexico's Baja Peninsula; Mexican sailors report being stalked by the "Black Demon."
Investigating increasing reports of Bigfoot encounters from across the United States; using scientific methods to examine whether witnesses are seeing a known animal or the same creature described throughout history.
Investigating the history of eyewitness accounts of a 50-foot monster known as Ogopogo sighted in Lake Okanagan in British Columbia, Canada.
An expedition investigates controversial evidence that might confirm a history of sea monster sightings off the coast of Florida.
Expeditions search for the Goliath grouper off the coast of Florida and a monstrous fish with frightening teeth beneath the icy surface of lakes in Minnesota.
The Tasmanian tiger was thought to have become extinct 80 years ago, but eyewitness reports and scientific research might indicate that the creature is on the verge of making a comeback.
The team embarks on a dangerous search in the Sea of Japan and along Australia's Great Barrier Reef to investigate reports of a jellyfish invasion that threatens to turn oceans into deadly places to swim.
Investigating reports from Papua New Guinea of a terrifying monster with a 20-foot wingspan known as the "Demon Flyer" that some people think might be a prehistoric pterosaur.
Investigating reports from India of encounters with a ferocious half-man, half-ape creature dubbed the monkey man.
Across the world, people are reporting increasingly frequent encounters with frighteningly large crocodiles.
Searching the jungles of Central Africa for an elusive monster said to resemble an enormous, long-necked and four-legged saurpod dinosaur believed to have gone extinct 65 million years ago.
Investigators try to compile and analyze evidence to prove that the elusive monster known as sasquatch exists, including videos, tracks, prints and maps of sightings.
A team searches for feral dogs to uncover where they live and determine how dangerous they are in the wake of reports of predatory packs of canines attacking people.
In the 1940s and 1950s, strange humanoid forms are spotted flying above North American towns, bringing waves of panic.
Investigating reports from Florida of encounters with potentially vicious wild chimpanzees; searching U.S. swamps and wilderness areas for wild chimps.
Large cats with a taste for flesh might be prowling parts of America; investigating reports of big black cats stalking and killing deer in New York state; probing whether dangerous exotic cats are on the loose.
Searching the sea for huge and aggressive albino sperm whales that inspired the novel "Moby Dick."
The team makes an epic ascent in the Himalayas in search of the Abominable Snowman, which witnesses claim is a ferocious nocturnal creature that attacks people and slaughters their animals.
Investigators interview victims of vicious wild boar attacks, examine evidence and team up with specialists to search for gigantic wild hogs.
In 2007, the residents of Bolivia, N.C., start losing pets and farm animals to an unknown creature with a taste for blood.
Paranormal investigators hoping to prove the existence of ghosts use high-tech equipment at the Lizzie Borden house, scene of an infamous 19th-century double murder.
People seek evidence of a Bigfootlike creature, the Ohio Grassman, a nest builder that sometimes attacks people.
Investigating reports of huge, man-eating snakes of 50 feet or more in length in Venezuela; pet pythons escape, multiply and grow huge in the Florida Everglades.
Eyewitnesses allege that a strange black beast is at large on the moors of England and killing livestock; an expedition team interviews the witnesses, analyzes the evidence and attempts to find out what is truly prowling the English countryside.
Investigators hunt for the Texas Chupacabra, a beast blamed for draining livestock of their blood; accounts vary from describing the beast as looking like either a reptile or a deformed dog.
An expedition along the Klamath River into Indian reservation land uncovers Native American "Hairy Man" stories and cave art dating back more than 1,000 years that indicates knowledge of the truth behind the Bigfoot legend.
New Englanders experience a vampire scare during the 1700s; investigators use the latest technology to analyze historical evidence and study people today who say they are vampires.
Divers probe the depths of the North Pacific in an attempt to confirm sightings of a 20-ton octopus, a boneless horror said to be massive enough to attack and sink boats.
Northern New York's Monster of Whitehall is described as a sasquatchlike creature that stands up to 8 feet tall and makes a sound like a woman screaming.
Searching for a Canadian creature dubbed "Cressie" said to be lurking around the bottom of Lake Crescent in Newfoundland; witnesses report seeing an outsized eel or perhaps something entirely alien to science.
Investigating reports of a hairy wild man said to roam mountainous and forested regions of China's remote Hubai province; Chinese authorities collect more than 100 unidentified hairs.
Investigating horrific bear attacks and strange bear remains; expeditions go to Alaska and New Jersey, where bears are becoming more aggressive.
A team returns to the Sea of Cortez with improved technology in hopes of confirming a sighting of a 100-foot squid some 1,000 feet below the ocean's surface.
An expedition hunts for a monster-sized, predatory spider in South America and investigates reports from the Middle East about giant arachnids.
The bull shark, one of the deadliest predators in the ocean, can tolerate fresh water and has been known to swim hundreds of miles upstream; shark sightings ranging from Illinois to the Louisiana bayous and the St. Lawrence River.
One team travels to Australia's Blue Mountains in search of evidence that the huge megalania lizard isn't really extinct while another expedition studies its closest living cousin: the Komodo dragon.
An expedition armed with high-tech surveillance and detection equipment stakes out a remote cabin in Canada that has been under attack by a creature that might be a sasquatch.
An expedition searches for Champ, a dinosaurlike creature that some say they have seen in Lake Champlain.
An expedition investigating a report of a Bigfoot attack at a Canadian fishing cabin finds blood and tissue samples said to be from the beast.
An expedition travels to the Sea of Cortez off Mexico's Baja Peninsula to use specially designed lures with built-in cameras in hope of spotting a giant squid 1,000 feet below the surface.
Investigating a rash of giant bird sightings in Illinois, Texas and Alaska during the 1970s; Indian beliefs in huge Thunderbirds.
An all-female expedition journeys to Washington state hoping to lure a Bigfoot within range of their cameras; scientists study Bigfoot evidence, including 1967 film footage.
Two expeditions try to trap mysterious dog-killers; a beast described as a mutant kills pets in Maine and Minnesota in 2006.
Mountain lion attacks on people make headlines across the U.S., but some people say they have seen something else: a mysterious big, black cat.
Probing reports from Louisiana and Florida of the "Swamp Creature," a red-haired beast that stands 7 feet tall and smells like rotten eggs; tracking the creature with bloodhounds.
Soviet dictator Josef Stalin may have planned to cross humans with apes; mankind and Mother Nature try to combine the intelligence of humans with the strength of apes.
Cryptozoologists use special equipment to try to shed light on reports of rods: torpedolike creatures that fly so fast they cannot be spotted by the naked eye.
A team searches the rain forest of Sumatra for mystery ape orang pendek, said to have a humanlike face.
Eyewitness reports from Wisconsin and Michigan tell of a tall and hairy man-beast described as a "dogman."