A late afternoon buying spree erased a triple digit loss in the Dow , sending stocks higher for the day.

Like a good thriller, the ending wasn’t what most investors expected.

Early in the session, Corporate America announced a slew of billion dollar deals but the M&A mania couldn’t get the bulls to budge.

Then, a big buyer came into the market Monday afternoon and scooped up tech options. The move sent bargain hunters into a frenzy.

Buyers even shrugged off the action in oil , which tumbled, below the psychologically important $70/barrel level on Monday on concerns of a global slowdown.

What gives? What must you know?