It appears that an unknown man, by scientific means, has made himself invisible.
5 seconds sound clip from the The Invisible Man (1933) movie soundboard.
You can hear this line at 00:41:22.906 in the Blu-ray version of the movie.
Quote context
[...]
- Now, at all costs, we must avoid a panic spreading.
- Now get away to your districts at once, and send me a note of your headquarters.
- And remember, he'll leave tracks, even if he himself is invisible.
- I must interrupt the dance music for a moment. I have an urgent message from police headquarters.
- Earlier this evening, we broadcast a report of an invisible man. The report has now been confirmed.
- It appears that an unknown man, by scientific means, has made himself invisible.
- He has attacked and killed a police inspector and is now at large.
- The chief of police appeals to the public for help and assistance.
- The Invisible Man works without clothing. He will have to seek shelter.
[...]