SDCL § 21-11-1: Fraud or mistake as ground for revision.

When through fraud or mutual mistake of the parties, or a mistake of one party which the other at the time knew or suspected, a written contract does not truly express the intention of the parties, it may be revised on the application of a party aggrieved so as to express that intention, so far as it can be done without prejudice to rights acquired by third persons, in good faith and for value.