St. Louis County Police tell Patch the robbery happened around 9 p.m. Monday night at the Dollar Tree store in Creve Coeur at Olive Road and Ross Avenue.
Investigators say the man hid inside the store and waited for the two employees to lock up, then he took them to a back room, tied them up and robbed them at knifepoint.
He made off with an undisclosed amount of money, plus the two employees cell phones and keyes.
Investigators said the suspect then fled on foot.
For most Maryland Heights residents, the Creve Coeur Dollar Tree is the closest location to home. The location sits just a few miles from city limits.
Police are searching for a man who is about six feet tall and 200 pounds. He was wearing a black shirt and khaki pants at the time of the robbery.