Five mainland thugs, led by Lam Wai, plan a day trip to HK for a jewellery shop robbery, which goes horribly wrong. While basically animals loyal only to each other, they occasionally show a little humanity.
This film is simply stunning, although the first half-hour is rather slow. The later City On Fire was clearly inspired by this one, and it seems likely that John Woo used this film as a blueprint for movies such as The Killer.
If anything, Woo's gunfire ballads look pretty tame compared with Long Arm's straightforward documentary feel and brutal honesty.
Clearly a big success, this film spawned at least three sequels I could trace.
Ultimately very grim, but highly recommended.