Back to Sid's filmography: This is a re-scripted version of the third in a four part series on the history of cave diving, which was based on Martyn Farr's book The Darkness Beckons. The film starts with a reconstruction of Mike Boon's successful dive into Ireby 2, followed by a reconstruction of Mike Boon's and Alan Clegg's maypoling operations on the far side of the Langstroth Cave sumps. This is followed by an account of Alan Clegg's death in the Lancaster Hole terminal sump, and Mike Boon's attempt to rescue him. The action shifts to South Wales where a reconstruction of Charles George's and John Osborne's breakthrough into Ogof Fynnon Ddu 2 is shown. The effect of the Mossdale Caverns incident on diving in the Yorkshire Dales is discussed. The film concludes with reconstructions of Tom Brown diving with a broken arm in Ingleborough Cave and Gaping Gill during the making of The Lost River of Gaping Gill The film includes interviews with Mike Boon and Tom Brown. The divers involved in the film include Rupert Skorupka, Mark Robson, Nicholas Gem, John Adams, Tom Brown, Mike Wooding, Dany Bradshaw, and Dave Savage. It was originally shown on BBC One on September 28 1989.