Real estate developers sold lots of what turned out to be undevelopable swampland to around 3,000 purchasers. A group of the disgruntled purchasers (the Rodriguez plaintiffs) sued the sellers, banks, and others involved in the transactions (defendants) for alleged violations of the Interstate Land Sales Full Disclosure Act (ILSFDA) and several other federal statutes. The Rodriguez plaintiffs attempted to have their suit converted to a class action, but the court did not allow it. Olga Gonzalez and a group of other purchasers who had been unable to join the Rodriguez action (the Gonzalez plaintiffs) then brought a separate action against the same defendants. The Gonzalez plaintiffs had the same lawyers as the Rodriguez plaintiffs and alleged very similar claims. The Rodriguez plaintiffs eventually lost at trial. The court then dismissed the Gonzalez action on the grounds that it was barred by res judicata. The Gonzalez plaintiffs appealed to the United States Court of Appeals for the First Circuit.