Kastorff, a general contractor, submitted a bid to the Elsinore School District to make additions to their school building. He added up his figures incorrectly and submitted a bid just under $90,000 when he meant to bid just under $99,500.
The approximately $10,000 difference was quite significant in 1960, the time of the case. He discovered his mistake the next morning and tried to revoke his bid, but the school district insisted that it was too late, that it had already accepted his bid.
The question is whether Kastoroff's unilateral mistake excuses his contractual obligation to the school district.
The following question and answer sequence explains the sense in which the mistake is unilateral.