When we got home from the roleplaying convention on Thursday, Smudge did what she often does and slipped out the front door as we came in and onto the stairs to sniff around - but this time I did not notice. The first I gathered was when we heard a mournful 'mrouwl!' through the door after I had closed it! Once I realised that it was not just a neighbourhood cat outside and that Smudge was nowhere to be seen, I opened the front door again - only to have her streak inside faster than lightning and then zip around the flat for the next few minutes as if scared of her tail! Neil picked her up and we tried to calm her down but she was frantically wiggling for a few minutes longer.
Unsurprisingly, every time we have come in the door since then, she has not left the safety of the flat to even be a curiosity-cat for a second!