But a wild, mysterious, romantic intruder has appeared on the scene.

They did not know who this mysterious intruder menacing them could be.

Had they had another visit from the mysterious intruder?

Gregor felt it his duty to discover all he could about the nature of the giant and mysterious intruder.

They were not eager to pursue a mysterious intruder in the dark.

There they joined the half dozen men who were already speculating on what had become of the mysterious intruder.

Her twin sister Valerie was murdered in 1966 at the family home by a mysterious intruder.

"Young man, you are violent," answered the mysterious intruder, in a low voice.

As for the mysterious intruder, we have guards everywhere.

Had the mysterious intruder been dealt with, perhaps by Q?