"Fog," as the title implies, is drenched with misty atmosphere, another splendid Jeremy Burnham script effectively rendered by director John Hough. Cobblestone streets, flower sellers, organ grinders, and a man specializing in knife sharpening, all evoking 19th century London as a modern day 'Jack the Ripper' stalks the members of a disarmament conference. The first half sets up the murders, while the second has The Avengers investigating an exclusive club devoted to the legendary Gaslight Ghoul (the entire episode takes place in one fog shrouded night). Guy Rolfe had appeared in many shows on both sides of the Atlantic (Karloff's THRILLER), and played the title role in 1961's "Mr. Sardonicus," while Nigel Green, previously seen in a smaller part in "The Winged Avenger," tops the guest cast as the club president, who also happens to be an expert surgeon. Also featuring Paul Whitsun-Jones ("Man with Two Shadows," "The Wringer," "Room Without a View"), Norman Chappell ("Dance with Death," "Dead of Winter," "The Gilded Cage," "Dial a Deadly Number," "Murdersville"), David Lodge ("Epic"), John Garrie ("The Winged Avenger"), Arnold Diamond ("Who's Who???"), Frank Sieman ("Six Hands Across a Table"), and William Lyon Brown ("Death's Door").