Note 1: きます (to come) vs. いきます (to go)

In English: A: Where are you now? B: I'm at McDonald's. A: OK, I'm coming [there] now. In Japanese: A: いま、どこですか。 B: マクドナルドに います。 A: じゃ、いま、 いきます。 ( きます is unacceptable.)

Japanese きます = Someone comes to the location where the speaker is.
If the subject is the speaker ("I"), きます means "come back here."

私｛わたし｝は　あした　きます。(= I will come [back here] tomorrow.)
ブラウンさんが　きます。(= Brown will come [here].)

English "come" = Someone comes to the location where the listener or speaker is.

Choose the best Japanese equivalent for the following:

1. I will come to Mr. Brown's office tomorrow. (Speaker is at home now.)
   私は あした ブラウンさんの オフィスに（きます／いきます）。
2. I will come to my office tomorrow. (Speaker is at home now.)
   私は あした オフィスに（きます／いきます）。
3. I will come to my office tomorrow. (Speaker is at her own office now.)
   私は あした オフィスに（きます／いきます）。

Note 2:

かえります means that you are "returning home" (i.e., where you belong). If you are returning to your own home (うち), you should use かえります and not いきます.

うちへ (or に)　かえります	"to go/return home"
うちへ (or に)　いきます	Unacceptable if you are "returning to your own home." Acceptable if you are "going to someone else's home."

If you say としょかんへ かえります, you are not only saying "I'm going back to the library," but also implying that the library is a kind of "home" where you belong.