The story is about Yasubei (Tsumasaburo Bando) and his uncle Kayano. Yasubei is a Samurai but a very lazy drunkard. He always tries to avoid his uncle, Kayano, who wants Yasube to go straight. However, one day, Kayano had a feud with one of other Samurais, and was forced to have a duel. But it turned out to be 2 to 20 fight, with no prospect for Kayano to win. Even though Kayano being an able swordsman, it is a simple murder. Then, Yasube, heavily drunk as usual, came back to his room to find the note from his uncle about this demise. (This clip starts at this point.) Yasubei realizes how lousy he has been, takes a bucket of water to shake off alcohol, and dashes to the rescue his uncle.
A bit of a background. This story was so popular in first half of twentieth century that audience did not need explanation. It is based on the actual incident in 1694, but Koudan readers and theater troops provided the stylized and exaggerated version of the story frequently. It has been made into the feature film twice. Once by Daisuke Ito in 1928, and this one by Masahiro Makino in 1937.
In later years, Makino said about this dashed-to-the-rescue scene, "I overdid it."