In an attempt to reach an agreement with France, Adams appointed a diplomatic commision of three men (including John Marshall: the future chief justice) to Paris in 1797.
They hoped to meet with Charles Maurice de Talleyrand, the French foreign minister, but were instead secretly approached by three unnamed go-betweens, who were later referred to as X, Y, Z.
They demanded a loan of 32 million florins + a bribe of $250,000 for the privilege of merely talking with Talleyrand (intolerable terms that caused negotiations to quickly break down)