The ‘Damsel in Distress’ theme is a common one throughout all of Western storytelling. Typically there is a helpless maiden being tied up and tormented by an evil villain or monster, when along comes a hero to save her in the nick of time; think Perseus and Andromeda, St George slaying the dragon, Snow White, or even King Kong movies.
This theme was a popular one with the Pre-Raphaelites during the Victorian era too. The Pre-Raphaelites felt that Raphael, and artists after him, had corrupted art and that a return to the naturalistic paintings and romantic themes of medieval art was necessary. Depictions from stories of Arthur and the Knights of the Round Table were particularly popular, and I assume that this painting is of Sir Galahad who saved many a maiden while on his quest for the Holy Grail. We see the damsel in distress in the foreground while in the middle ground Galahad returns his sword to its sheath after just having slain a villainous knight.