But certainly one used to dealing with unknown threats.

He added, "Officers are facing previously unknown threats and great danger."

In the face of this unknown threat, it felt safer to hold onto each other.

No matter how her soul screamed out in protest, she had to get Cassie away from this new, possibly unknown threat.

The mood was volatile, dangerous, edgy; faced with an unknown threat.

They receive it and send in Delta Force to deal with this unknown threat.

We have to delay it and oh look, here's an unknown threat coming at them from the other side of space.

After all, this man might be part of the unknown threat.

As he swung his left arm up to defend himself from some unknown threat, Tucker grabbed it.