Despite having the day off from school, Councilman Jolon Clark’s two children found a way to be very productive Monday.

They solved a years-long mystery. And their reward? Another mystery.

Whenever Chloe, 11, and Logan, 13, came to Clark’s office, the two would try to open the big, vintage safe that has sat unopened and intriguing for years. On Monday, they finally did, only to find another set of locked doors.

“I was on the phone and they were turning the dial and they popped the door open,” Clark said.

The two were at his office because of a teachers’ workday. They brought a stethoscope, wrenches and screwdrivers to help break into the safe.

“They said they were turning the dial, using the stethoscope, and the dial just stopped,” Clark said. “That never happened. They tried the handle and it opened up.”

The old safe — which Clark said features an anti-dynamite patent from 1885 — has been a source of intrigue since Clark moved into the office four years ago. It had been reduced to an extremely heavy and ornate TV stand as Clark and his staff wondered what was inside. Clark said he had been warned that it probably couldn’t be moved, even though it has wheels, out of fear that the heavy thing would crack the granite floors in the building.

As of Monday morning, Clark said the children were working to break into the second set of doors.