The Promise - S3-E11
Revealing mistake: When Richard jumps out of the 6th floor window, in the interior shot we see that he lands right at the base of the window's frame, as his body bounces back from the impact, but when Brackett looks out the window Richard is lying on the ledge, which is much farther down than the window's bottom frame.
Answer: I believe you are speaking of the old man, Mr. Wilson. He's played by J. Pat O'Malley.
Bishop73
Correct, it was J. Pat O'Malley...he also played the grandfather with his grandson when their rocket exploded, and also played "Old Bill" in the episode with Ann Prentiss, where Gage saves the little girl from the burning tree house, and her mother falls in love with him.