The expression, “to cover [one’s] tracks,” refers to the act of someone intentionally concealing or hiding his or her activities, whereabouts, or any evidence for the purpose of avoiding discovery. Typically used in mystery stories, this idiom evokes the image of a nefarious criminal eliminating his “tracks” to avoid being caught by the police.
“The killer attempted to cover his tracks of the murder he had committed by hiding the victim’s body in the forest.”
“The cheating husband tried to cover his tracks by paying only in cash whenever he went out with his mistress. Unfortunately for him, his wife was suspicious of his infidelity and had hired a private detective.”
*Note that in situation 2, the cheating husband attempted to conceal his affair by using only cash to cover his tracks.