“Hah!  I knew it.  Bauer, eh?  And to-night he’ll be sitting at one of those back windows, his ears stuffed with cotton, watching to see your plant blown up.  We must have the constables here right away.”

“On what charge?” says I.  “That two of the kitchen maids was seen in their own back yard?  You know you can’t spring that safety-of-the-realm stuff over here.  The police would only give us the laugh.  We got to have something definite to tell the sergeant.  Let’s go after it.”

“But I say!” protests Cecil.  “Just how, you know?”

“Not by stickin’ here, anyway,” says I.  “Kick in and use your bean, is my program.  Come along and see what happens.”

So first off we strolls past and has a look at the place.  It’s shut in by a rusty iron fence with high spiked pickets.  The house sets well back from the sidewalk, and the front is nearly covered by some sort of vine.  At the side there are double gates openin’ into a grass-grown driveway.

I was just noticin’ that they was chained and locked when the Lieutenant gives me a nudge and pulls me along by the coat sleeve.  I gets a glimpse of the square-built female waddlin’ around the corner of the house.  We passes by innocent and hangs up in front of a plumbery shop, starin’ in at a fascinatin’ display of one bathtub and a second-hand hot-water boiler.  Out of the corner of my eye, though, I could see her scout up and down the street, unfasten the gate, and then disappear.

“Huh!” says I.  “Kitchen company expected.”

“Or more conspirators,” adds Cecil.  “By Jove!  Isn’t this one now?”

There’s no denyin’ he looked the part, this short-legged, long-armed, heavy-podded gent with the greasy old derby tilted rakish over one ear.  Such a hard face he has, a reg’lar low-brow map, and a neck like a choppin’-block.  His stubby legs are sprung out at the knees, and his arms have a good deal the same curve.

“Built like a dachshund, ain’t he?” I remarks.

“Quite so,” says Fothergill.  “See, he’s stopping.  And he has a bundle under one arm.”

“Overalls,” says I.  “Plumber, maybe.”

“Isn’t that a knife-handle sticking out of the end of the bundle?” asks the Lieutenant.

So it was; a butcher knife, at that.  He has stopped opposite the double gates and is scowlin’ around.  Then he glances quick at the house.  A side shutter opens just then and a dust-cloth is shaken vigorous.  Seein’ which, he promptly pushes through the gates.

“Ha!” says the Lieutenant.  “A signal.  He’ll be the one to attach the fuse and light it, eh?”

Well, I admit that up to that time I hadn’t been takin’ all this very serious, discountin’ most of Cecil’s suspicions as due to an over-worked imagination.  But now I’m beginnin’ to feel thrills down my spine.

What if this was a bomb plot?  Some sort of bunk was being put over here—­no gettin’ away from that.  And if one of our shell factories was in danger of being dynamited, here was my cue to make a medal play, wa’n’t it?