Thirty-five years after a foundational test of particle physics was first imagined, researchers at the BESIII collaboration in Beijing have returned to it armed with quantum entanglement — a tool that barely existed when the question was first posed. By measuring the electric dipole moment of the Lambda hyperon with unprecedented precision, they have opened a window through which the universe might reveal whether our best theory of matter and forces is truly complete, or merely the most accurate map we have drawn so far. The result does not yet overturn the Standard Model, but it sharpens the