From G. K. Chesterton's The Man Who Was Thursday: A Nightmare.
WHEN Gabriel Syme found himself finally established in a chair, and opposite to him, fixed and final also, the lifted eyebrows and leaden eyelids of the Professor, his fears fully returned. This incomprehensible man from the fierce council, after all, had certainly pursued him. If the man had one character as a paralytic and another character as a pursuer, the antithesis might make him more interesting, but scarcely more soothing. It would be a very small comfort that he could not find the Professor out, if by some serious accident the Professor should find him out. He emptied a whole pewter pot of ale before the professor had touched his milk.
I am having trouble understanding the sentence in bold.
Edit to provide more context: Gabriel Syme had just been accepted into the inner circle of a secret society of which the professor is a member. After the first meeting, he found the professor had been following him around the town. They are now at a bar, and Gabriel Syme is worried that the professor might have guessed his identity.