Frank hadn't even managed to get an hour of surveillance at the hospital in before he'd gotten another note from Sirius, and what he'd seen was entirely normal, so far as he could tell. Dolohov had attended to his patients. They all seemed more healed when he left them than when he started to work with them. That didn't mean much, of course; if this really was the guy holding a student hostage, then this was no doubt his cover for whatever sick and twisted business he was up to.
Of course, he wouldn't be able to keep his cover with a possible patronus on the way to summon him to battle, so he had to give it up early. But he caught a peek at the schedule for the trauma ward before leaving, so it wasn't all useless: he had a lead on when Dolohov would be back here at the hospital, if he kept to his schedule. It was something, anyway.
Ideally, he would have been away from everyone at this point, but when he looked back at his rustling journal, he saw that Sirius's plan seemed to be off, too. Well, this was all clearly going amazingly smoothly. Best laid plans, and all that. After a moment's hesitation, he Apparated to Sebastian's place. With no idea what was going on tonight, it was as good a place as any to spend the evening, and he'd take the drinking slow so that he'd be ready to jump up at any time. Sebastian wasn't a member of the Order - his politics had always been relatively neutral, so far as Frank knew - but he was one of Frank's very best friends, the only one that had been trusted with his very darkest secret. Because he'd been there, and helped him through it. Frank had no reason to believe that it would be a problem if a Patronus showed up in the Smith's house, and he was a cautious man.
Landing, he found his friend in the armchair, and dropped into the other. "Blimey," he said. "You want help with that as well as the whiskey? I've picked up a few tricks over the years, you know."