be (sitting) on (one's) tail

To follow close behind someone or something. Why is this guy sitting on my tail when I'm already going over the speed limit? The cops are definitely on our tail now—we have to turn ourselves in!

Common Names:

Name	Pronounced	Usage
Saga	SAH-gah (Swedish)	Norse Mythology, Swedish, Icelandic
Gemma	JEM-mah (Italian), JEM-ə (English), KHE-mah (Dutch)	Italian, Catalan, English (British), Dutch
ThÉRÈSe	te-REZ	French
Alvah	AL-və (English)	Biblical
Sloan	[sləun]
Benedikte	-	Danish, Norwegian