Zach explores the unpredictable and terrifying phenomenon of Sinkholes to determine just what causes them. He visits a Florida man whose brother was killed. See more in Season 1, Episode 6, "Sinkholes." #InSearchOf Subscribe for more from In Search Of and other great The HISTORY Channel shows: https://histv.co/SubscribeToHistory Find out more about the show and watch full episodes on our site: http://www.history.com/shows/ Check out exclusive The HISTORY Channel content: History Newsletter: www.history.com/newsletter Website - http://www.history.com Facebook - https://www.facebook.com/History Twitter - https://twitter.com/history Hosted and executive produced by Emmy-nominated actor Zachary Quinto, and inspired by the iconic 1970s’ franchise, the series will examine unexplained phenomena from all over the world. UFOs and paranormal mysteries remain relevant as the Pentagon recently acknowledged a secret UFO program which investigated sightings of UFOs from 2007 – 2012. The HISTORY Channel® is the leading destination for award-winning original series and specials that connect viewers with history in an informative, immersive, and entertaining manner across all platforms. The network's all-original programming slate features a roster of hit series, premium documentaries, and scripted event programming.