Devil in the Details

I came across the phrase but have nowhere to find out the meaning. If anyone could be of help, I would be grateful.

Thanks
Rosemary

It means that small errors may add up to big trouble!
For instance, I read recently about a husband who was able to defraud his own wife through a very tiny mistake by a notary.
The notary's failure to cross out the letter "(s)" in "person(s)" and to line through the word "are" in "is/are" can made it easy for the conniving husband to forge his wife's signature on a document and then add her name to the notarial certificate.
The "devil" was surely hiding in the details of this mistake!