A fleeting secondary tone was detected in the GW250114 signal, offering a rare chance to test the “Kerr solution,” which describes a rotating black hole using only mass and spin. Excitingly, the mass and spin values from this overtone matched those from the fundamental tone. If they had differed, it would imply that additional properties are necessary to describe a black hole, but a match confirms that, at least for this black hole, no other details are needed.