Health experts have three days to work out how Covid spread from a traveller
Testing has linked the cases to a returned US traveller - but there is a missing link
The positive case is a man in his 50s, but he had no contact with quarantine
Restrictions are set to be lifted on Monday at 12.01am - but link must be found
He visited 14 suburbs in Sydney while infected with Covid-19 last weekend
Masks are mandatory, dancing banned and only 20 people are allowed in a home