Military and Government leaders say the coincidence supports their suspicion that Soviet submarines were responsible for the mysterious activity during much of the 1980's.

Or how there was some mysterious activity at the Tucker facility?

Whatever his mysterious activities had been that evening could not affect the case.

People he knew, people he had never seen, came and went about him, engaged in mysterious activities.

Khozak himself took over then with his account of the discovery of the mysterious recent activity in the mines.

At least that explains the mysterious activity in the ruins of the factory.

A stockbroker who had had other rather mysterious activities.

Because all the events that had overturned the world had their origin in his mysterious activities.

Their mysterious activities must be threatened by too many Federation personnel nearby.

In the Hall outside, the green lamps glowed, and the machines hummed with their ceaseless mysterious activity.