The film co-stars Jackie Chan, Yuen Biao, Sibelle Hu, Richard Ng, Charlie Chin, Eric Tsang, and Stanley Fung.

Undercover cop Muscles (Jackie Chan) enlists his childhood friends, the "Five Lucky Stars", to travel to Japan to help him catch a yakuza group.

A corrupt Hong Kong cop (Lam Ching Ying) flees to Tokyo to join his fellow mobsters, whose headquarters are secretly built under an amusement park (filmed in Fuji-Q Highland).

They refuse to aid the police, but the supervisor cunningly sets up a false story in the media that accuses the five of robbing a bank of millions of dollars, blackmailing them into helping.

After a prolonged battle at the bowels of the amusement park, the criminals lose and the Lucky Stars receive a place to live back at Hong Kong as their reward.