Formal decrees of rescission and cancellation may be obtained in equity in cases where no plain, adequate and complete relief can be had at law.1 While the courts agree in this abstract statement of principle, a number of difficult questions arise in its application. On the one hand, the party who has been defrauded may seek cancellation in equity, and the question will be presented whether the right to interpose the defense of fraud in an action at law is a clear, adequate and complete remedy which will prevent him from obtaining such relief in equity. On the other hand, the party who has been defrauded may attempt to avoid such transaction at law without obtaining a decree of cancellation in equity, and the question will be presented whether the transaction is one which can be avoided for fraud informally, or whether a formal decree in equity is necessary. While the existence of this power is undoubted, it is said to be an exercise of an extraordinary power, which must be used with care and discretion.2