The Termination of Skynet (1st attempt) refers to the event where Sarah Connor tried to destroy the Cyberdyne Systems building in order to stop Judgment Day and to prevent Skynet being created. She failed and was shot and arrested. She lost custody of her son, John Connor. She was then sent to Pescadero State Hospital because people thought she was mentally ill.
A T-800 and John rescue her from Pescadero, on the run from a T-1000. The three of them attempt to destroy Cyberdyne and succeed.