Powell eventually realizes that the selenium source contains unforeseen danger to the robot.

The unforeseen danger in this case was the slyness of the attack.

"I'm certain you only had them charged in the event we encountered some unforeseen danger."

Many unforeseen dangers may be lurking in the wings.

"Always on the lookout for the unforeseen danger."

What could have been more natural than for them to withdraw into the desert to retain their powers after having encountered the unforeseen danger?

Her road lay through the woods, where an unforeseen danger lay in wait for her.

She always seemed to pick just the right spot when unforeseen danger lurked.

Cheap perfumes can have unforeseen dangers too, such as skin allergies.

As it happened, she fell from power the week before the connection could be made, an unforeseen danger.