One of the most unlikely ideas for a movie of all time, for sure. Bad Guy Chen Kuan-Tai isn't such a bad guy really, until some other bad guys kill his wife and chop off his sons hands. This makes him bitter against the world, and he turns into something of a tyrant. He also gets a pair of iron hands made for his son, and trains him in kung fu... and his son becomes an even worse tyrant. This pisses off our heroes, who try to teach them a lesson. But they underestimate the father & son's powers and fail, and in return they cripple each one in a different way. However, not to be deterred by being blind, deaf/dumb, legless and brain damaged respectively, the heroes train their kung fu to overcome their disabilities, and then go back to try again.
The idea is quite an interesting way to give each of the fighters a different style to use, although you won't buy the genuineness of their disabilities for a moment, and in the end their fighting all boils down to displaying the actors' incredible athleticism. The leaping, diving, rolling etc is all quite remarkable, although the fights are waay too choreographed as a result of showing it all off. You can't help but think that if they'd just stand there and hit each other the final showdown would all be over much quicker.
The movie's as old school as it comes, so that ought to be enough for you to decide if you'd like it or not. If you want to see some really impressive physical performances, it's a good bet. If you want a more rounded movie experience, probably not going to be found here.