“This” was a pair of bent and rusted steel rods, although it did not take a very close examination to see that they had originally been two parts of a still-longer whole. The longer of these two sections, about eighteen inches from the still-attached ball joint to its broken end, was pitted from long exposure to the elements; grains of sand still nestled in the rough surface. Holmes fingered its uneven end: not merely broken, but half sawed through, then twisted hard to shattering.

The other piece was slightly shorter, just over a foot long, and although it, too, was rusted, its lack of pitting and sand indicated that it had spent its life in a slightly more protected environment. One end was a twin with that of the longer piece—half sawed, half wrenched apart. Its other end, however, was neatly, and freshly, sawed through.

Hammett gestured at the tidy end of the shorter piece. “I didn't think we really needed to haul the whole thing around, so I just cut off the hunk we needed. Seemed to me the two ends said it all.”

Holmes laid the two pieces of rod on the table, the broken end of the rusted one resting against the broken end of the cleaner.

“I have long feared it might be something of this order. Yes, Mr Hammett, I know what this is. I spent some time as a garage mechanic in Chicago, just before the war broke out. A little case for His Majesty. That's a brake rod, or rather the better half of a brake rod, and I agree, you were right to cut it off—as far as evidence is concerned, there's no need to drag around a piece of steel half the length of a motorcar. Which side of the motor was it from?”

“The left.”

“So whoever did it knew they would be travelling south on that road.”

“I . . . Yes, I suppose they would have.”

“No supposition involved. Failure of the left-side brake rod under pressure would cause the motor to swerve to the right, and with that hill-top turn it didn't even require an on-coming motor to break the rod.” Russell's father would have braked hard at that spot in any event—without the other motor, without two squabbling children in the back. Mary Russell's disagreeable behaviour had nothing to do with it.

“Whoever did it was clever,” Hammett agreed. “And according to my guy, if it'd been cut all the way through, your Mr Russell would never have made it as far as the top of that hill without crashing.”

“Although I'd have thought he'd had to have been a remarkably cautious man to drive all the way from San Francisco with brakes in that condition.”

Hammett's starved-looking face relaxed into a satisfied grin. “They stopped for lunch in Serra Beach. That little town about a mile before the hill.”

“Parking the motor out of sight?”