It was his move.
Since, years ago now, as the Gray Seal, he had begun to work with HER, that unknown, mysterious accomplice of his, and the police, stung to madness both by the virulent and constant attacks of the press and by the humiliating prod of their own failures, sought daily, high and low, with every resource at their command, for the Gray Seal, he had never been in quite so strange and perilous a plight as he found himself at that moment.

To preserve inviolate the identity of Larry the Bat was absolutely vital to his safety.

It was the one secret that even she, who so strangely appeared to know all else about him, he was sure, had not discovered--and it was just that, in a way, that had brought the present impossible situation to pass.
In the month previous, in a lull between those letters of hers, he had set himself doggedly and determinedly to the renewed task of what had become so dominantly now a part of his very existence--the solving of HER identity.

And for that month, as the best means to the end--means, however, that only resulted as futilely as the attempts that had gone before--he had lived mostly as Larry the Bat, returning to his home in his proper person only when occasion and necessity demanded it.

He had been going home that evening, two nights before, walking along Riverside Drive, when from the window of the limousine she had dropped the letter at his feet that had plunged him into the affair of the Counterfeit Five--and he had not gone home! Eventually, to save himself, he had, in the Sanctuary, performing the transformation in desperate haste, again been forced to assume the role of Larry the Bat.
That was really the gist of it.