William goes to saddle up stables in the middle of the night when no one is around and takes five saddles. william's crime is

William's crime is larceny.

There are different types of thefts, including robberies, larcenies, and burglaries. Robbery is when you steal someone's belongings using threats, without their consent, but with their knowledge. On the other hand, larceny occurs when you steal someone's belongings without them knowing, which is the case here with William and him stealing 5 saddles furtively.