The Outer LIMITS 1963 S1 E16 Controlled Experiment

Deimos and Phobos One are two Martians – whose names also happen to be those of Mars' moons– the latter being a researcher who wants to understand the concept of murder, as it is apparently exclusive to Earthlings (they are portrayed by actors Carroll O'Connor and Barry Morse, respectively, who play their characters as a sort of Holmes-and-Watson team). Upon his arrival on Earth, Phobos One contacts Deimos, whose 'cover' is working as a pawnbroker in a large American city. The duo, inconspicuously, investigates a shooting that is about to take place in a downtown hotel lobby that resulted from a love triangle, predicted and then reported by Martian Central Control. Using a machine that can manipulate the flow of time in a manner much the same as one might do with recorded video, they review this same event over and over again. They rewind time in order to watch the incident unfold at various speeds, forward and backward. Finally, they slow the passage of time down to such an extent that the participants seem to be standing still, the bullet suspended in flight, so that they can examine all of the nuances that, at "normal" speed, pass by too quickly for adequate, scientific observation. Phobos One is unable to simply remain a passive observer, and finally gives in to the temptation to tamper with the scenario and alter the outcome; he arranges the scenario so that the bullet is deflected at the last moment, preventing the murder from ever taking place. Phobos decides to remain on Earth indefinitely, finding that he enjoys life as a human being.