When filmmaker Josh Fox received an unexpected offer of $100,000 for the natural gas drilling rights to his property in the Delaware River Basin, on the border of New York and Pennsylvania, he resisted the urge to accept. Instead, he set off on a cross-country journey to investigate the environmental risks of agreeing to the deal.

Gasland is Fox's urgent, cautionary and sometimes darkly comic look at the largest domestic natural gas drilling campaign in history, which is currently sweeping the country and promising landowners a quick payoff.

However, as Fox discovers, the drilling process, called hydraulic fracturing or fracking, was exempted by the Bush-Cheney Energy Policy Act of 2005 from the United States' most basic environmental regulations, including the Safe Drinking Water Act  and the Clean Air Act. Across the country, in major cities such as New York, Los Angeles and Dallas-Ft. Worth, where drilling is slated to take place or is already occurring directly in water-supplying areas nearby, a crisis looms that could affect millions.

Part verité road trip, part exposé, part mystery and part showdown, Gasland follows director Fox on a 24-state investigation of the environmental effects of hydraulic fracturing. What he uncovers is mind-boggling: tap water so contaminated it can be set on fire right out of the tap; chronically ill residents with similar symptoms in drilling areas across the country; and huge pools of toxic waste that kill livestock and vegetation.

Gas companies have now turned their attention to the massive Marcellus Shale Field, where Fox's Pennsylvania home rests. Stretching from the Catskill region of New York State to West Virginia, the so-called "Saudi Arabia of natural gas" is also home to the country's largest unfiltered watershed, supplying water to millions of Americans, including the residents of New York City. Thousands of leases have already been purchased by drilling companies, prompting a public controversy.

Fox reveals alarming facts about America's natural gas industry. In 2005, Congress passed the Energy Policy Act, championed by then-Vice President Dick Cheney, which exempted fracking from numerous long-held environmental regulations such as the Safe Drinking Water Act. Natural gas companies have installed hundreds of thousands of rigs in 34 states, drilling into huge shale fields, tight sands or coal bed seams containing gas deposits trapped in the rock. Each well requires the use of fracking fluids - chemical cocktails consisting of 596 chemicals, including carcinogens and neurotoxins, as well as one to seven million gallons of water, which are infused with the chemicals. Considering there are approximately 450,000 wells in the U.S., Fox estimates that 40 trillion gallons of chemically infused water have been created by the drilling, much of it left seeping or injected into the ground across the country.

Gasland features interviews with: ordinary citizens whose lives have been irreparably altered by hydraulic fracturing; scientists like MacArthur "Genius Award" fellow Wilma Subra, who warns of the dangers of arsenic poisoning from drinking groundwater affected by fracking fluid; and government officials on both sides of the issue, including John Hanger, Pennsylvania's secretary of the Department of Environmental Protection, who minimizes the effects of fracking, but refuses to drink a glass of water from an affected well, and Manhattan Borough President Scott Stringer, who laments the possibility that New York City's safe, great-tasting water will become a thing of the past.

The public remains largely unaware of the potential dangers of hydraulic fracturing, while state and local environmental agencies do not have the resources to fully investigate or regulate the gas industry. In many instances, residents have received huge tanks of water to replace their water wells, but the smell and lingering illnesses of people and livestock attest to the damage done. Anyone able to secure compensation from the gas companies must sign non-disclosure agreements that prevent them from bringing lawsuits or informing others of their experiences with natural gas drilling.

The fight against hydraulic fracturing has now moved to Congress, where lobbyists are trying to prevent legislation that would require the chemicals used in the fracking process to be subject to the Safe Drinking Water Act once again.

Gasland is an HBO Documentary Films presentation of an International WOW production; a film by Josh Fox; edited by Matthew Sanchez; produced by Trish Adlesic, Josh Fox and Molly Gandour; written and directed by Josh Fox.