Prowler (noun)

A person who moves stealthily, especially at night, in a suspicious manner.

Origin:

From the middle english word prouleren, meaning 'to roam about'.

Examples:

1. The police were alerted by a neighbor about a prowler in the area.
2. The security system scared off the prowler and protected the family's home.
3. The prowler was caught on camera by the store's surveillance system.
4. The sounds of the prowler outside her window made her heart race.
5. The prowler turned out to be a lost cat, much to the relief of everyone involved.