Queen – “The Trap” [Campaign 1, Mission 4]

Masters of walkthroughs! I'm following your instructions: I took the boots of levitation and built the mage guild. But when I cross the bridge, a cutscene starts showing that the Elf I was supposed to team up with has already been killed. And the game restarts at the beginning of mission 4. Could it be that I spent too much time preparing for various preliminary battles? And I didn't manage to team up with the Elf in time. Where can I find him? Thank you in advance.