Trailing by a point with 5.5 seconds remaining, Seekamp inbounded from the Capitals' baseline to Lauren Nicholson before sprinting the full length of the court.

Nicholson zigzagged her way through the Capitals' defence before finding Seekamp under Adelaide's basket and the Lightning co-captain did the rest, slotting the biggest basket of her career in front of 3702 screaming fans at Titanium Security Arena.

Seekamp finished with a team-high 19 points while import Nia Coffey contributed 14 points and 10 rebounds.

For the Capitals, Kelsey Griffin confirmed her standing as the competition's premier player with 24 points and a whopping 23 rebounds while Kia Nurse (16 points 10 boards) proved a valuable ally.

Capitals co-captain Marianna Tolo, the sole remaining player from the Caps' 2009-10 championship successes, was busy early before Nurse caught fire.

She notched nine straight Canberra points - including a remarkable banked three-pointer off an inbounds pass - to fashion a 23-19 quarter-time advantage.

The Lightning got to within two points in the second term before an unsportsmanlike foul against Coffey on Griffin reinvigorated the Caps.

Griffin was in everything as the Capitals went on an 8-0 run to move 10 points clear before Seekamp's trey on the half-time buzzer reduced Canberra's lead to 44-37.

Griffin waged a lone hand in the third period, scoring Canberra's first nine points but she had no support and the Lightning gained the upper hand, moving ahead when Coffey sank two free throws before Nurse stroked a triple on the three-quarter-time buzzer to give the Caps a slender 56-55 advantage.

Canberra increased the buffer to 68-61 and looked like taking home the silverware in a sweep before Adelaide made their charge, paving the way for Seekamp, fittingly, to provide the last-second heroics and set up a decider in the capital on Saturday.

Australian Associated Press