Mrs Bortz’s car explosion transforms a quiet pre-dawn departure into a violent roadside crash, then becomes a crucial clue in the investigation of the Carpathian Hound’s disappearance. What first sounds like a gunshot is identified as a bomb: John Murphy used the blast not to kill Mrs Bortz, but to frighten her into delaying the pool’s drainage while he pursued the hidden Hound.

The Blast and Crash

The incident begins after Mrs Bortz’s sedan backs into the street and starts forward slowly. In the pre-dawn stillness, the boys and Fenton Prentice hear an explosion and a scream. Prentice jumps up, and Jupiter Jones rushes to the window. Down the street, the sedan veers first left and then right, with smoke pouring from beneath the hood. It strikes the kerb hard enough to blow out both front tyres, then crashes head-on into a hydrant.

The impact snaps the hydrant off at ground level, sending water up around the car. Mrs Bortz screams repeatedly, still rigid behind the steering wheel and staring straight ahead. Pete Crenshaw calls for the fire brigade. The boys hurry to the wreck while John Murphy, in a bathrobe, runs toward it and Sonny Elmquist comes out wearing a coat over his pyjamas. The boys pass them, wade through ice-cold water, and force their way through the cascade from the broken hydrant. Jupiter reaches the sedan and pulls at the door, but it is locked. The rush to help is thus met with another immediate obstacle: Mrs Bortz is visible inside, but the boys cannot simply open the car and reach her.

From Apparent Shot to Bomb

The first interpretation is uncertain. A plain-clothes policeman says that if anyone shot at Mrs Bortz, the shot missed. Jupiter insists that he heard a shot, or perhaps an explosion, just as she began driving away. The distinction matters: the damaged car could suggest an attack by gunfire, but the examination of the wreckage points elsewhere. There are no bullet holes.

Under a torch, the officers find scraps of paper and what appears to be singed cotton wadding across the engine block. The radiator hoses are scorched, and the fan belt has snapped. The plain-clothes man concludes that the sound was not a shot but an explosive device, a bomb placed beneath the bonnet. The sedan, listing over the broken hydrant and lit by the breakdown truck’s headlamps, is taken away to the police garage. The loud, conspicuous crash has converted an uncertain report into physical evidence of deliberate sabotage.

Murphy’s Purpose Revealed

The explanation comes later, when Jupiter reconstructs the attack. Both Murphy and Alex Hassell had been away from home during the burglary, and both had heard Mrs Bortz announce that she intended to drain the pool. Jupiter recalls that her announcement startled Murphy; Murphy then drove off later that evening. Alfred Hitchcock proposes that Murphy may have gone to obtain the explosive, and Jupiter explains that he went to a friend who manufactured chemicals.

The bomb was wired to Mrs Bortz’s car, but Jupiter says it was not really deadly. Its intended effects were noise and smoke: enough to upset her and make her forget about draining the pool for a day or two. That short delay was the device’s real objective. The explosion therefore belongs to the larger struggle over the Hound’s concealment; it is a diversion designed to preserve Murphy’s opportunity, not an attempt to destroy the car for its own sake.

Investigative Reversal and Significance

The attack also helps explain why Murphy initially seems to be another victim rather than the culprit. After a fire in Murphy’s apartment, Jupiter considers whether the burglar might have set it to remove potential witnesses, and suspects Hassell. The ransom instructions overturn that theory: the money is to be left in the park waste-paper bin at exactly five o’clock, when Hassell feeds the cats. Jupiter reasons that a burglar who was Hassell would have chosen another time. The car bomb’s later explanation fits this revised account: Murphy had a concrete reason to delay the pool’s drainage, and the explosive provided precisely the brief interval he needed.

The scene’s movement from a suspected shooting to a bomb, and from apparent danger to a calculated delay, gives the explosion its double significance. It is a frightening physical emergency for Mrs Bortz and the people trying to reach her, but it is also evidence that exposes the practical design of Murphy’s deception. The broken hydrant, locked car, damaged engine, smoke, and noise make the scheme visible in the very moment it temporarily succeeds in diverting attention from the pool.