d I was after him
like knife. I tracked him to Knightsbridge without much difficulty,
excepting the one of avoiding being spotted, but there that happened by
the merest accident. He was passing under the scaffolding outside the
church they're pulling down there, and he's so tall he knocked his hat
off. I admit I was too close. He saw, and must have recognised me; but I
shouldn't have recognised him if I hadn't seen him start out. He was
wearing a false beard and spectacles!"

"That's proof positive," said ingenuous Mr. Upton, under his breath.

"Well, I confess it's something like it in this case; but it was a very
awkward moment for me. I hadn't to let him see I knew him, nor yet that I
was following him, and the only way was to abandon the chase as openly as
possible. It was then I decided that it was no use leaving poor old
Mullins in pawn to the police. I redeemed him without delay. We went
back to my new rooms together, which I needn't tell you I liked so much
that I brought a suit-case and took them for a week. Of course, as we had
lost the run of Baumgartner, the next best thing was to watch for his
return. Mullins took that on while I got some sleep; when I awoke the
Park Lane murder was the latest, and I won't say I didn't suspect who'd
done it. Perhaps I didn't tell you he had his camera with him as well as
beard and goggles, and all three figured in the first reports."

"But all this time you had no idea my boy was in the house?"

"None whatever; we saw the girl once or twice, but that was all until I
wired last night. What I never saw myself was Baumgartner's return; but
in the afternoon I sent Mullins round to another road to try and get a
room overlooking the place from the back. Well, the houses were too much
class for that; but one was empty, and he got the key and risked going
back to prison for the cause! Suffice it that he set eyes on both man and
boy before I sent that wire."

"And you left my son in that murderer's clutches a minute longer than you
could help?" It was a previous incarnation of Pocket's father that broke
in with this.

"You must remember in the first place that I couldn't be in the least sure
it was your son; in the second, if murder had been intended, murder would
have been done with as little delay in his case as in the others; thirdly,
that we've nothing to show that Dr. Baumgartner is an actual murderer at
all, but, fourthly, that to raid his place was the wa