[Update 05/30/16: this review sucks. I will try to redo it soon.]
Set in the 1800's, Yuzo Kayama is a young doctor fresh out of school. He plans on making a ton of duckets being a doctor to the shogunate, but is sorely disappointed when he's assigned to a public clinic. He immediately butts head with the head doctor, Dr. Kyojo Niide (Mifune), also known as Red Beard. At first the new doctor just sits in his room drinking and pouting, but then he starts to loosen up as he hears the heartbreaking stories of the poor and observes their sad lives up close.
As suspected from the beginning his heart thaws and after six months of guidance by Red Beard, the young doctor becomes not only a great doctor, but a great man, who is more interested in helping people who truly need help than making money by catering to the rich.
Simplistic view, yes, but still a beautiful movie. It's also the last film of Kurosawa's great period and his final film with Mifune.