He was not prepared for this. Everything was falling apart and he'd always thought that every step of the way, no matter how bad things got, @Avella would be here with him through it all. There was no contingency plan for a life without her.
On the third night without her return, Hagar had begun to worry and search. Now, the sixth day was closing and he had not found a single sign. It was not conceivable to him that Avella would just abandon them, especially not their remaining children. If she had gone to find Iseldir, she would have told him as much, wouldn't she? What if she was hurt somewhere, hoping for help and he just wasn't looking in the right places? Where else was left that she could have gotten to in such short time?
It wasn't just her, even. Ra had not been seen either, Clouse obviously distressed by the fact and quick to demand Hagar take action for her as well. He tried, hoped maybe they were together, but why wouldn't they be home by now then? And if poor Ra was alone out there... her brother was very valid in his concerns.
Panic was building in his chest, and as he returned back to the old Ridge den from a day of scouring to an empty cavern, he climbed back out and began to pace. They needed to act together, like a pack even if their chances of truly being one dwindled every day. Hagar lifted his head and howled, loud and strong, asking with clear urgency for every wolf still with them to meet him here.