This is by far one of the best films by Hayao Miyazaki and by Studio Ghibli, in my opinion. It has action, adventure, romance, characters to fall in love with, to pity, and to hate. It's got a lot all wrapped up into one, and it's definitely one to see if you haven't seen it already.
This story follows a young woman named Sophie, who lives during a time when war is about to take place. She tries to act wise and smart, when really she's rather frail inside. Her mother is more excitable than she is. The story starts out with Sophie having to meet up with her sister, Lettie, but as she's walking down an alleyway she's hassled by two guards who probably would have taken advantage of her had Howl not come around. He uses his magic to make the guards leave, but then the two are quickly followed by henchman of the Witch of the Waste. They manage to escape, even barely, but Howl takes Sophie to her sister - by walking on air!
Though she's not seen by anyone, she tells her sister what happens and Lettie warns her that Howl is dangerous and she shouldn't go near him anymore.
When Sophie arrives back home, she locks the door to the hat shop, but the Witch of the Waste comes in and puts a curse on her when she "defies" the Witch. Sophie is then turned into an old woman of about 80 years old, and can't believe it. She goes off to find someone who can help her - Howl. Along the way she meets Turnip-Head and manages to get into Howl's Moving Castle.
The story plays itself out by Sophie claiming to be the new cleaning lady, while Markl and Calcifer try to dissuade Howl from letting her stay there. But Howl lets her anyway because the castle really could use a good cleaning.
During her time there, Sophie slowly starts to break the spell over her and ends up falling in love with Howl. There are a lot of mishaps and things that go wrong along the way - like Howl using magic that transforms him to fight for the war and he'll soon turn into that creature unless he stops. At one point he turns into a giant beast that Sophie tries to tell she loves despite everything going on, but Howl won't hear of it - and the spell on her was almost broken, too!
You learn about Howl's past, about how he gave up his heart to Calcifer, and about how the Witch of the Waste desires it.
The group - Sophie, Markl, Calcifer, and Howl - all grow closer together as time passes, working with each other and learning from each other as they go. Even though trials face them, they manage to pull through in the end.
As I said before, there are characters to love and hate, to pity and laugh with, or at. But as I don't want to give too much of the movie away, you'll just have to determine for yourself whether or not you want to see this fantastic film. The movie is rated PG.