Crabs are evil looking sods but surely if you ran at high speed in a straight line away from them you would probably be fine, as they meander sideways like Space Invaders or me walking home from the pub after a night out.
Then again maybe Crabs are in fact masters of disguise that rely on the element of surprise. (never trust a crab with a moustache.)
I've never read a Crabs novel so would probably be the first one to fall victim to a psychotic crustacean.
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MIKE: I've got it! Peter Cushing! We've got to drive a stake through his heart!
VYVYAN: Great! I'll get the car!
NEIL: I'll get a cushion.