A relocking mechanism that blocks the path of a bolt within a lock assembly is presented. The relocking mechanism comprises a breakaway member that is repositioned when the lock assembly is attacked by some mechanical means, such as impact applied via a hammer and punch to the lock housing through a spindle hole in a door. The breakaway member prior to attack holds a preloaded relocking plunger clear from bolt movement. When the breakaway member is repositioned upon attack, the plunger is free to move under a biasing force into position so as to block the bolt thus keeping the lock in a secure locked state regardless of the state of the locks default blocking mechanism.