Pat Clarke fired an extra-time winner to complete a stunning fightback against Alloa that puts Clyde in the Division One play-off final.
Jimmy Gibson headed Clyde ahead, but Brown Ferguson's 35-yard drive and a Derek Fleming free-kick appeared likely to relegate the Cumbernauld side.
It was 3-1 when Dusan Bestvina failed to clear a Kyle McAuley effort.
But Gary Arbuckle fired home and headers from Willie Gibson and Gary McSwegan sent the tie into extra time.
The 6-5 aggregate win means Clyde visit Airdrie United, who defeated Raith Rovers, in Wednesday's first leg of their play-off final.
Rovers and Alloa remain in Division Two.
Clyde: Hutton, Higgins, Bestvina (Michael McGowan 48), William Gibson, Masterton, Wilson, James Gibson (McKay 72), Ruari MacLennan, Bradley (McSwegan 46), Arbuckle, Clarke.
Subs Not Used: Fagan, Cherrie.
Booked: Wilson, William Gibson.
Goals: James Gibson 30, Arbuckle 64, William Gibson 68, McSwegan 84, Clarke 111.
Alloa: Jellema, McClune, Townsley, Forrest, Fleming, Grant, Brown Ferguson (Scott 55), McKeown, McAuley, Brown (Andrew Ferguson 76), Agnew (Hodge 30).
Subs Not Used: Coakley, Bruce.
Booked: Brown Ferguson, Townsley, Grant.
Goals: Brown Ferguson 40, Forrest 42, Bestvina 46 og.
Att: 1,200
Ref: M Tumilty
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