When two unfamiliar wolves meet they express curiosity, fear or aggression. It is important to know who the other wolf is!
An unfamiliar wolf that intrudes on a flock's territory is met with hostility and the flock usually attacks it. If the trespasser feels insecure, it expresses submission or fear.
The intruder usually runs away. But it sometimes happens that the strange wolf is killed. Getting killed by other wolves is, next to starvation, the most common cause of death among wild wolves.