Abstract: In 2018 the EDGES collaboration announced a detection of 21 cm hyperfine absorption at redshifts between about 15 and 20. The signal may indicate that the hydrogen gas at cosmic dawn was significantly colder than predicted. I'll describe a new scenario that might solve the mystery: hydrogen oscillates into a mirror state over the course of the cosmic dark ages, leaving the remnant gas cooled and the anomaly imprinted. This proposal differs markedly from other BSM scenarios in both the relevant microphysics and the implications for model building and cosmology.