[1] Between 1959 and 1973 the first 38 volumes of this series were systematically revised as part of a project directed by Harriet Adams, Edward Stratemeyer's daughter.

This story begins with Frank and Joe Hardy driving home along Shore Road when they have an accident with a dragster.

After they arrive home their father, Fenton Hardy, tells them about a new case he has taken on for Alden Automotive Research and Development Company, with which he would like the boys' help.

Mr. Hardy explains that Mr. Alden believes someone is trying to steal the plans for a secret new engine he is designing, and that two of his racing cars which were equipped with new engine had strange accidents in which their windshields suddenly "crazed" (turned an opaque white), just after passing a road sign warning “DANGER”.

Frank and Joe start by working undercover at Alden’s shop, while their friend Chet Morton takes an interest in jet propelling his bicycle, which leads to humorous results.

At the shop, the boys meet Barto Sigor and learn that he has a twin brother Vilno who recently quit Alden’s employment.

The boys immediately suspect that the twins may have swapped spots so that Vilno can gain access to the plans for the new motor.

The Hardy boys eventually figure out where Barto is hiding, but when they reach the mansion hideout, they are suddenly "frozen in their tracks" by a "powerful invisible force".

That very same day, Joe sees another machine swing in from the road and edge into the parking space, its bumper nudging one of the automobiles at the top of the incline.

Joe saves them by braking the automobile; however, the owner of the auto starts hurling accusations at the younger Hardy, who stands his ground, and with the help of Frank, thwarts him.

They decide to investigate the route by which they'd reached the Seneca field, and they barely avoiding being hit by a speeding truck driver.

Mr. Hardy, a famous detective, decides to take his sons to Vilnoff's home for an alibi-check, where they learn that he is sailing for Europe in a few days.

However, unlike Fenton Hardy, Frank and Joe don't trust Vilnoff, so they scan the outskirts of his home.

When they reach the crossroads, Frank suggests they take a shortcut through the field, which involves climbing up a wooden fence.

However, they don't escape scot-free, as the barbed wire pokes holes on their clothes, and a mad goat trails them out.

While going to Bayport, they stop by a gas-station to eat something, but the hostile proprietor seems to want to get rid of them when a man in a green truck comes by.

They ask for petrol, but halt when they see a bunch of men making multiple trips to the Bayport woods with briefcases.

The story ends with the Hardy brothers reading the will of Aunt Gertrude's distant relative, Jonathan Hood, who died in Kentucky two months ago.