A man walked into the Rite Aid on Dyer Avenue wearing a skeleton mask and threatened the clerk with a knife, police said.
But that wasn't enough to scare the clerk, who refused to give the suspect any money despite repeated threats and demands.
Eventually, the man gave up and left the store.
Police said the suspect left footprints in the snow towards the Arlington section of the city, but the trail went cold.
Police continue to investigate.
The incident happened Wednesday around 9 p.m.