It all began with occasional but persistent rumours about the extraordinary things seen by travellers on lunar orbiters that had suddenly drifted off course. They reported passing through a gap in time where the accepted rules of chronological order ceased to apply, and seeing things that were familiar, yet exceedingly strange. At first, the scientific community proclaimed these external worlds to be highly improbable. But eventually they could no longer deny the evidence that other parts of the universe were anachronous.