The Madman Theory by Ellery Queen

I suppose he can drive Earl’s car back to San Jose.”
    â€œThat solves one problem. Oh, I’d appreciate your communicating with me at the Fresno County Sheriff’s office if any further ideas occur to you. And please tell the others the same.”
    Collins stood in the doorway as the four men got into Earl Genneman’s white station wagon.
    Kershaw drove, Vega sat beside him, James and Retwig in the rear seat. The car moved off down the road and was soon lost to sight.
    Collins sat on the front bench. Two hundred yards through the trees he could glimpse children playing on the white sand beach that fringed Kings River.
    Phelps came to join him. “What do you think now?”
    â€œI don’t like the madman theory, but it’s the only one that makes any sense. There aren’t any hermits living out in the wilds?”
    Phelps grinned. “We call them fire-lookouts. They wouldn’t shoot anyone, except possibly someone with a Roman candle.”
    â€œThe state I’m in now, I’ll give any theory serious attention.”
    A dark green pick-up pulled up in front of the cabin; a ranger jumped out with an envelope for Phelps. “License numbers, sir, covering Wednesday, Thursday, Friday and Saturday. We’ve arranged each day’s take in order.”
    â€œThanks, Walt. Don’t go just yet—I may have a little job for you.” Phelps turned to Collins. “You plan to check on each of these cars?”
    â€œCorrect.”
    â€œMay I make a suggestion?” Phelps indicated the nearby campground. “We can look over the cars here and in the other campgrounds, and eliminate the obviously improbable.”
    Collins hauled himself to his feet. “Let’s take a look.”
    They crossed the road to the cedar-shaded campground. Among the trees stood tents, with cars parked nearby.
    They walked from car to car; when Phelps identified a car as having entered on one of the four critical days Collins inspected its interior, peered into the corresponding tent and queried owners. In this way twelve numbers were expunged from the list.
    Sergeant Easley had returned from the parking area with notes on the fourteen cars he had found parked. Of these fourteen, only seven proved to have entered the park during the critical period, and the remaining were at least temporarily dismissed from consideration.
    At the Cedar Grove Trailer Park and Public Camp Grounds #2, the process of elimination continued; then Phelps drove Collins and Easley to the General Grant Camp Grounds, where further cars were stricken from the list.
    The time was now four-thirty. Collins telephoned headquarters for transportation back to Fresno, then he and Easley visited the cocktail lounge where, three days before, Earl Genneman, Bob Vega, Red Kershaw, Buck James and Myron Retwig had rendezvoused. The bartender remembered the group but had noticed nothing unusual.
    An hour later the patrol car arrived; Collins and Easley climbed in and were conveyed back through the forest of giant redwoods, down the mountainside, and over foothills where scrub oak now cast long shadows across the valley, and into the warm summer evening.

4
    On Wednesday morning Collins wrote a laconic report of the murder and took it into the office of Captain Bigelow. Much to Collins’ relief, Bigelow was out and he was not subjected to one of the captain’s “analyses” of the report. Bigelow was a hard man to work under; he had a manner of quick decision that impressed his superiors but strained the fortitude of his subordinates. Bigelow’s offhand suggestions, delivered in staccato, the subordinate could either heed or ignore. In either event Bigelow took credit for success and masterfully rebuked failure.
    Collins had learned to maneuver. His strategy took one of two forms: he wrote his reports either in excessive detail, noting every contingency, possibility and qualification, so that of necessity