Why is Mr. Smith in a good mood?

(W: Woman  M: Man )
W: You seem to be in good mood, Mr. Smith.
M: Well, today’ s my thirty-seven birthday, and a friend is having a party for me tonight.
W: That is really wonderful.
M: Maybe you know her. She lives in the building too. Her name is Lucy Smith.
W: I am not sure. What does she look like?
M: Well, she’ s got wavy brown hair, and she is a little taller than you. She is about my age.
W: Oh, Professor Smith7 I met her once.
M: Well, I have to get back to my apartment.
W: What is the matter? You look upset.
M: I think I locked my keys in my apartment.
W: Uh-oh, You’ve got a real problem. The Andersons are lot home now.
M: Do you know when they will be back? Maybe I will wait here the pool.
W: I don’ t think that’ s a good idea. They went away for at least one week.
M: At least one week! What am I going to do? I can’ t go to a party dressed like this.
W: Wait! I just remembered! Can Johnson in apartment 201 take over Mr. Anderson’s duties this week?
M: Great! Thank you for your help.