Ghost Hunters' season four finale takes the TAPS team to Portsmouth Harbor Lighthouse and Fort Constitution in New Castle, NH. The 48-foot cast-iron tower was erected in 1771, with the grounds covering approximately 2 acres including Fort Constitution and the Keeper's Quarters. After years of late night reports from the Coast Guard and other witness accounts, the members of the Friends of The Portsmouth Lighthouse want to know if the lighthouse and surrounding grounds are truly haunted. Jason and Grant will be facing one of their most interesting challenges as they explore the Portsmouth Harbor Lighthouse, the Fort Constitution and the Keeper's Quarters.