Doctor Who: Where's My Sonic? 3 The Master's Plot

Liz Shaw used to work for UNIT as a scientific advisor. She never thought she'd come back. But when she learns that John Pertwee's Sonic Screwdriver is gone she knows she has to return. But who has stolen it? Meanwhile Sergeant Benton has feelings that he needs to confess to the woman of his dreams, Jo Grant. However when the letter falls into the hands of his superior, Captain Yates, things take a turn for the unexpected. Harry Sullivan though just wants revenge in anyway he can get it. The Brigadier is invited to the opening of some secret building. As the hunt is on for the Sonic how is all of this connected? The Master has a new plot that he's sure will destroy Pertwee and his friends forever. Will Matt Smith and the gang get there on time? Or will The Master's plot pull through? Most importantly the question must be asked... who will remain the master of their domain?