In this frame they are not happy because they live in a old and small apartment. Della is not happy because she only has $1.87, she doesn't have a lot to buy Jim's gift. Jim is not happy because he has to sell his watch.
In frame they are giving there gifts to each other. When Della opens her present, there where combs in the box. When Jim opens his present there was a watch holder in the box.
In this frame the falling action is they are sitting down to eat there dinner. They still love each other. They traded they things to get each other a gift that they wanted to give each other.