I've needed to know, and here we both are with time on our hands.

No one had ever needed to know what he did.

Why would he have needed to know her room number?

You just need to know how to look for them.

If these are the only three things you need to know, why the first two books?

Nothing else you need to know about until we get inside.

She needs to know what I need, and where to meet me.

What you need to know once you've decided to start trying for a baby.

First I need to know which one of us is wrong.

The Power does not need to know any particular thing.