What gets me is that Keaton shelved this film for not being good enough. If I was a comedian or a filmmaker today, I'd sell my soul to make something half as great as The High Sign.
Most silent shorts are long on gags and short on plot -- character works in pawnshop, character climbs building, etc. --but here Keaton packs in an awful lot of locations and characters, and a not insignificant amount of story into nineteen minutes.
The short ends with Keaton cavorting through a tricked-out house booby-trapped and full of secret passages. The physicality and visual inventiveness on display here is second to none. And yet Keaton proves in the first half that he can also wring humor out of the simple act of hanging his hat, which he does multiple times.
(Also, this is truly the only way to christen a new 50" plasma TV, with a 90-year-old, black-and-white, silent film.)