This film was based on an episode of The United States Steel Hour (1953) called "Fearful Decision" that first aired live on June 22, 1954. It was so well received it was restaged on May 10, 1955. A film was made from the drama called Ransom! (1956) that was released by Metro-Goldwyn-Mayer.
Is the Theatrical Version the only version available? Is there a longer one?
During the glorious days of the laserdisc an Extended Version was released in the States and Japan that features nearly 18 minutes of new footage. Even today those laserdiscs are the only way to see this longer cut that involves several extended plot scenes. A detailed comparison between both versions with pictures can be found here.
When Det. Shaker "rescues" the kid, the kid listens to him as he identifies himself as a cop. Later when Shaker is in Mullen's house to collect the reward, the kid listens to him also, but this time he recognizes his voice and pees in terror, which tipped Mullen thus giving the next twist in the story. But why didn't the Kid recognize him the first Time?
Shaker might not have said anything to Sean when he first entered the room. When the SWAT team burst in, all Sean hears Shaker say is, "I'M A COP! I'M A COP!" in a desperate, exasperated tone. Sean may not have recognized the voice then because his emotions were mixed at that time given the relief he would have felt. Plus hearing Shaker tell SWAT he was a cop will have thrown him off. Sean could easily have believed Shaker.