I was in Marleybone when I got to level 29. Then Ambrose popped up for help. He said "Sorry to bother you, but I need help, urgently." Or something like that. Then the notice disappeared, and I went to Merle Ambrose... But he just said "Keep on searching. We need to know everything we can about Malistaire's plans."
Merle Summoning Players without Reason: Sometimes Merle likes to check in with his students, however we've noticed lately that he's been calling on our young Wizards every time they gain a new level. Don't worry, he may not always have a quest for you, however it's a good reminder to visit him, as well as your Professors, on a regular basis.