Frenemy??

Two weeks ago the family next door returned from living in Reykjavík for a year. Their cat, Nemó, has been kept indoors since they arrived but today when I came home from my physio appointment, he was prancing around on top of a neighbours car.
A little while later when I opened the door to let Loðvík out, Nemó was sitting on the steps watching us, safely behind the glass railing. Loðvík hissed at this "new" cat and then they ran out into the parking lot.  Nemó tried to hide under a car but seconds later I watched them sprint south down the street. 

Loðvík returned home a few minutes later, seemingly unharmed...I didn't see his new friend...enemy?