Where a person lawfully does
anything for another person, or delivers anything to him, not intending to do so gratuitously, and such
other person enjoys the benefit thereof, the latter is bound to make compensation to the former in respect
of, or to restore, the thing so done or delivered.
Illustrations
(a) A, a tradesman, leaves goods at B’s house by mistake. B treats the goods as his own. He is bound to pay A for them.
(b) A saves B’s property from fire. A is not entitled to compensation from B, if the circumstances show that he intended to
act gratuitously.