you hear what old Welsby said about it? It looks uncommonly as if I
were the thief. You remember what you said the other night when we had
that feed, about seeing that man? D'you think there _is_ any one who
comes here at night and steals things?"

"Well, I'm certain I saw some one in the playground when I told you.
It was a man; but whether he comes regularly and goes into the shed I
don't know, but I think we ought to be able to find out."

"How?"

"Oh, some way or other; I'll tell you to-morrow." That night, long
after the rest of the house were asleep, the Triple Alliance lay awake
engaged in earnest conversation; and in the morning, as the boys were
assembling for breakfast, Diggory touched Acton on the shoulder and
whispered,--

"I say, we've thought of a plan to find out if any one goes into the
shed at night."

"Who's 'we'?"

"Why, the Triple Alliance; we thought it out between us. Sneak out of
the house directly after evening 'prep,' and meet me in the playground,
and I'll show you what it is."

At the time appointed Acton ran down the path, and found Diggory waiting
for him by the shed.

"Look," said the latter, "I've cut a little tiny slit with my knife in