MI9 must handle an epidemic of robberies committed from underground tunnels. They are dug using the MO of the incarcerated Mole. The team gets him to admit he has an accomplice, who co-build the digging machine and must be operating it alone, actually Luke Withers, who was hired by Skul. The Mole is enlisted to help trace and catch him, even though Frank fears he's too much of a flight risk. Meanwhile headmaster Flatley tries to stand up to his bossy deputy King, who literally took over his office.
—KGF Vissers