***SPOILERS*** After knocking off a Chicago bank of $80,000.00 the three collage boys Noel Mel & Phil, Ron Starr Denny Niels & Richard Tyler, drive their getaway car into Mrs. Josie Talaferio and her 6 month baby as the two were crossing the street leaving the two in critical condition at the local hospital. It's then that M Squad Let. Det. Frank Ballinger,Lee Marvin, sprang into action in trying to catch the creeps and bring them to justice. Feeling in some way guilty in what they did, by running over mother & child, it's decided by the collage boys to send $2,000.00 of the stolen bank money to Mr.Talaferio, Steve Gravers, to pay for his wife & child's doctor bills.
This in a way opens the door to finding the bank robbers because it leads straight to bank teller Joseph Rinehart, Jimmy Lydon, a very successful horse player who's suspected by Let. Det. Ballinger of having something to do with the robbery. That's by him living way beyond his means of being a $75.00 a week bank teller and among other things paying $250.00 a month for a luxury apartment, that almost $2,000.00 in 2014 dollars, on Chicago's west side. Ballinger thinks that it's impossible to win at the racetrack, due to personal experience, so the innocent as well as lucky Rinehart is suspected of being the inside man in his own bank's robbery!
***SPOILERS*** As it turns out Reinhart did have a somewhat connection in the robbery by him trying to romance dancing instructor Edna Reed, Carol Ohmart, who just happened to be the head of the robbery gang Noel's big sister! And even more she in fact planned and financed the robbery by getting the robbers the uniforms, as welders, to pull the robbery off! Let. Det. Ballinger in realizing that Reinhart had been played for a fool by Edna soon tracks down her brother at the collage that he's a student of to make the pinch! Only to get himself trapped in the science lab by Noel who plans to set the place on fire, with a bottle of acid, if he's to be taken alive. Not as smart as he thought he was Noel, and later his robber friends, were easily taken down by the police including his sis Edna by underestimating the Chicago police and especially Let. Det. Ballinger. That in him thinking that he and his friends, a bunch of bed wetting cry babies , were much smarter then they were which was a near fatal mistake on his part.