Mirror Image - August 8, 1953 - S5-E22
Question: Why would Sam need to warn Beth that Al would return and that he was an MIA? During the Vietnam episode the Pulitzer prize journalist took a picture of Al as a prisoner, so she already knew he was a prisoner.
Answer: In the finale, Sam leaps back to the episode "M.I.A." which is set in 1969. Originally, he failed to stop Beth from remarrying. However, the episode you're talking about, "The Leap Home", takes place in 1970. At the end of that episode, Al tells Sam that Maggie, the woman who took the picture of Al, finally got her Pulitzer Prize posthumously. But there's no indication when the picture of Al becomes public, or if Beth even saw the picture. However, if Beth did see the picture, or is aware Al is a POW, she's already moved on.
Bishop73