A man from Wollert, a suburb in Melbourne’s north, breezed into Melbourne from South Australian hotel quarantine, stopped at a 7-11, had a curry, shopped in Epping, took a train, and at some point, had a passing encounter with a stranger. Perhaps he coughed or spoke, or was simply breathing, but that was enough for a waft of aerosol to transmit COVID-19 to Melbourne’s missing link.