At Parker's Hill, New Hampshire, Jenny Swensen tests the limits of the M.A.X. suit — lifting boulders and measuring its strength-to-weight ratio — while her companion Andy monitors the telemetry equipment brought from M.I.T. Their field test is interrupted when a truck loses control on a muddy road above them and careens toward a house. Jenny, acting as Spitfire, flies to the rescue, catching the vehicle with the suit's electromagnetic clamp before it crashes. Witnesses spot the red armored figure, and the sighting makes the local news.
That night, at the mobile lab hidden in the woods — the late Karl Swensen's specially designed trucks — Jenny and Andy debate how much longer they can remain in hiding. Andy, a professor at M.I.T., worries about his classes; Jenny is unwilling to put their lives on hold, but equally reluctant to confront Fritz Krotze without solid proof that he had her father killed. At the M.I.T. dorms in Cambridge, Jenny's fellow students — Eduardo Giotti, Eric, Tim Ferris, and Teresa Roberts — watch the newscast and decide to take action. Giotti has built himself a pair of mechanical arms called "Strong-Arms," adapted from the M.A.X. servo-motor design. The group plans to infiltrate Krotze International's research complex, twenty miles outside Boston, where they recently went on a field trip: Teresa will bypass the alarm system, Giotti will handle the fence.
At Krotze International headquarters, Fritz Krotze watches the newscast and concludes Jenny has the M.A.X. suit. He summons his top systems engineer, Prof. Richard Faylen, and coerces him through personal leverage into deploying Behemoth — a Mark XII drone assault vehicle developed for the Department of Defense, operated remotely via a fiber-optic tether. Krotze wants it used to hunt down Jenny and recover the suit. Faylen, frightened but unable to refuse, boards a train transporting the tarpaulin-covered tank toward Parker's Hill.
Giotti, acting impulsively, jumps onto the moving train to spy on Faylen. He tears open a boxcar roof with his Strong-Arms but is beaten by Faylen's guards and loses contact with his friends. The others follow in a van. Meanwhile, Jenny calls a martial arts teacher for counsel about whether she can face Krotze. He advises her to identify her difficulty and confront the problem rather than hide from it. By dawn, Jenny and Andy are warned by the arriving Troubleshooters: the tarp is pulled back and Behemoth rolls off the flatcar, opening fire.
Jenny — as Spitfire — evades the tank's cannon and leads it away from the camp, buying time for the Troubleshooters to rescue Giotti. Faylen, operating Behemoth remotely from the train, attempts to negotiate, demanding she surrender the suit and lead him to her father's lab. His appeals to her father's memory only enrage her. Jenny destroys Behemoth's main cannon, then uses the M.A.X. suit's magnifying scanners to locate the fiber-optic tether — thin as a human hair — and severs it. With the signal cut, Faylen loses all control. Jenny rams the unmanned tank off a cliff, destroying it.
The Troubleshooters bring back a badly injured Giotti, who was beaten by Faylen's guards and has broken ribs. Faylen trembles with rage and fear at the loss of Krotze's weapon. Looking at her hurt friend, Jenny resolves to delay no longer: she is going after Krotze — now.
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