The story of The Haunted House is very simple: Mickey weathers a storm and seeks shelter inside a nearby house. Taking a look at just this frame of Mickey, you can clearly see how well defined and animated the character is. I think this is telling of the major growth taking place in the Disney Studio.
Once inside the house, Mickey soon discovers that he is not alone. He stumbles upon skeletons and a cloaked figure which try to scare him.
In a strange twist, the cloaked figure orders Mickey to play the nearby organ so that the entire household can dance to the happy melody. From this point, the toon turns into a song-and-dance routine.
An interesting note is that one piece of animation featuring the skeletons dancing is lifted straight from 1929's The Skeleton Dance, the very first Silly Symphony.
The Haunted House is currently on the banned Mickey shorts list, or Vault Disney. Towards the beginning of the film, Mickey is seen mimicking actor Al Jolson's now infamous black face routine in 1927's The Jazz Singer. Mickey's playful cries of "Mammy" are certainly not out of the ordinary for cartoons and movies from the late 1920s, but the depiction of black face is still considered rascist and morally wrong.
Another reason why this toon is banned is for another rascist depiction featuring two skeletons caricatured as Hasidic Jews. Again, this is not a gag uncommon in films from the this time period; in fact, many more depictions like this occur in other Disney shorts.
The Haunted House is full of great animation and special effects. The use of sillhouette, shadows, flickering candlelight, lightning, wind, rain, and bats flying straight towards the camera are prime examples of the growing sophistication Disney started to give its cartoons. This toon is certainly one of Mickey's best and a stepping stone for further more complex films.