The loss tarnished a record-setting performance by Toronto's Bashir Levingston, whose 129-yard missed field goal return late in the first half thrilled the Rogers Centre gathering of 29,157 and put the Argos ahead 15-10.
B.C. quickly erased that deficit. Two plays following Ian Smart's 76-yard kickoff return to open the second half, Smith scored from two yards out to put the Lions back ahead 17-15. Smith's one-yard run at 11:56 made it 24-15 and was set up by Cory Rodgers' 45-yard catch.
Jamall Johnson had B.C.'s other touchdown. Paul McCallum booted three converts and a field goal.
Arland Bruce III had Toronto's other touchdown. Noel Prefontaine had a single and Chris Hardy booted three converts.
True to his word, Argos coach Mike Clemons used two quarterbacks. Veteran Damon Allen started and was 14-of-18 passing for 130 yards and a TD over three quarters before Michael Bishop opened the fourth.
ishop pulled Toronto to within 24-22 with an eight-yard TD strike to Michael Palmer at 6:25 of the fourth. It came five plays after Leron Mitchell recovered Smart's fumbled punt return - his second recovery of the game - at the B.C. 40-yard line.
Bishop brought the house to its feet when he hit Andre Talbot with a 51-yard for what looked like a touchdown with just under six minutes remaining, but it came back on a holding penalty.
Bishop also drove Toronto to the B.C. 42-yard line with 1:22 remaining, but his pass on third down fell incomplete.
Levingston's electrifying return capped an exciting finish to what otherwise was a defence-dominated first half.
Levingston took McCallum's missed 32-yard try, ran straight a few yards, then broke to his right. After getting a block near the goal-line, Levingston ran untouched up the field and was so wide open that he merely jogged in from about 35 yards out.
Levingston's return broke the CFL record of 128 yards set by Calgary's Ron Hopkins in 1990.
Turnovers set up the other two first-half touchdowns.
Mitchell recovered Rodgers' fumbled punt return at the B.C. 11-yard line, setting up Allen's touchdown pass to Bruce at 13:03 that cut B.C.'s lead to 10-8.
The Lions' TD came when Barron Miles blocked Prefontaine's punt at the Toronto goal-line and Johnson recovered it in the end zone at 11:33 of the first. Prefontaine needed help leaving the field and when he returned, he missed a 33-yard field goal for a single 14 seconds into the second.
Hardy then came on to handle all kicking duties.
NOTES: Argos officials denied radio reports Thursday that slotback Derrell Mitchell, released last weekend by Edmonton, had re-signed with Toronto. Mitchell, a 10-year CFL veteran, spent the first seven years of his career with the Double Blue and was on Toronto's sidelines for the game . . . Running back John Avery, receiver Obed Cetoute, tackle Glenn January and linebacker Willie Pile were Toronto's pre-game scratches. Not dressing for B.C. were kicker Rob Pikula (who the Lions are trying to trade), defensive back Markeith Knowlton, offensive lineman Amariah Farrow and receiver Adam Nicholson . . . The Lions return 38 players from last year's championship team, including 20 starters.