Be was in the world of the Overlords: all around him, they were going about their mysterious business.

Her husband, Rich, runs some mysterious business that makes a lot of money.

Additionally, death is a mysterious business; after all, the only ones who know anything about it aren't around to share their knowledge.

We all remained silent, with our thoughts upon the new development which the mysterious business had taken.

After all, this mysterious business was on his mind.

I saw how the Morlocks were going about their mysterious business.

Proof enough that the creative process is a mysterious business.

Again the eyes were closed, the man was about his mysterious business.

So behind all this mysterious business there was the power of money.

He used the time until his food was ready to tend to some rather mysterious business.