But things are a little busy right now, with this unknown menace in Sector 3SR-5-42.

She had a feeling of some unknown menace that was threatening them.

Yes, they all had to be alert here, on guard against unknown menaces.

They had only the clothes on their bodies and the equipment they'd brought with them to use in fighting the unknown menace.

Major had told him of the unknown menace called The Shadow.

The far-flung beam might not only advertise their coming to some unknown menace ahead, but it could also be sighted readily by those following.

I put out a hand to grab the desk, seeking something solid to which I might anchor against this unknown menace.

What if some unknown menace descends upon us now, gathering force while we do nothing?

She could scare back sharks or allegations, but it wasn't smart to swim with an unknown menace.

To face such an unknown menace kindled one of the age-old fears of his own race.