Jon Taylor scored in the last few minutes as Peterborough United secured a deserved point against league leaders Gillingham at the ABAX Stadium.
Taylor popped up to fire home after Nelson had spilled Maddison's cross to secure a point for Posh in a game they dominated for long spells.
Gillingham scored during their best spell of the game through Adedeji Oshilaja but were denied all three points by Taylor's late finish.
Dave Robertson's men made a lively start and came close to the breakthrough inside two minutes as Jon Taylor's effort was saved with the legs of goalkeeper Nelson.
Jack Collison saw a shot blocked and Michael Bostwick headed a Maddison corner kick over as Posh dominated the early exchanges. Maddison then played in Washington on the counter attack, but his first touch was heavy and the shot was blocked.
Ben Alnwick produced a stunning save on five minutes to push away as Jonny Egan flicked a long throw towards the bottom corner with his head. Alnwick did well again on the quarter hour mark, pushing away a low effort from Houghton for a corner kick.
Maddison saw a low shot gathered comfortably by Nelson moments later after good hold up play from Washington. Houghton found the side-netting from a long throw on 19 minutes as Posh were sleeping at the set-piece.
Taylor, who was lively throughout the first period, saw a curler from 30-yards blocked as Posh continued to play some decent football.
On 42 minutes, Washington was cautioned for jumping into the defender following an aerial tussle.
Gillingham made a switch at the back with Emmanuel Osadabe introduced for Houghton. Dack fired wide from distance on 49 minutes after finding a pocket of space.
Vassell curled a 30-yard effort over the crossbar after Maddison blocked an attempted clearance from Egan.
Posh boss Robertson introduced Souleymane Coulibaly for Washington on 63 minutes. Dickenson was lucky not to escape a second booking on 66 minutes as he hacked down Maddison - referee Keith Stroud giving a final warning.
Coulibaly was denied by Nelson moments later, his chested effort from a Maddison free-kick clawed away by the goalkeeper.
Norris struck the crossbar with a swerving free-kick on 70 minutes after Bostwick gave away a needless free-kick.
Coulibaly tested Nelson from long-range on 71 minutes, the keeper doing well to hold the dipping strike. Collison was withdrawn on 75 minutes with Adebayo-Rowling moving into right-back and Bostwick pushed forward into central midfield.
Maddison saw a free-kick tipped over by Nelson on 80 minutes as Gills made another change with Cody McDonald introduced.
The visitors should have snatched a goal on 83 minutes as Norris was left in all kinds of space on the six-yard box, but his header struck the base of the post.
That miss didn't prove costly though as moments later they made it 1-0 as Adedeji OSHILAJA nodded home from close-range as Posh failed to clear a ball into the box.
Vassell cracked the underside of the crossbar with a stunning volley on 87 minutes before dragging the rebound wide as Posh came within a whisker of levelling the scores.
On 89 minutes, Posh drew themselves level, Nelson struggled to deal with a whipped cross from Maddison and there was TAYLOR to fire home the rebound into the back of the net.
Posh: Alnwick, Davey, Almeida-Santos, Elder, Bostwick, Taylor, Maddison, Collison (sub Adebayo-Rowling 75min), J. Anderson, Vassell, Washington (sub Coulibaly 63min). Unused subs: Henry, Brisley, Gormley, H. Anderson, Angol.
Gillingham: Nelson, Jackson, Egan, Houghton (sub Osadabe 46min), Hessenthaler (sub Loft 61min), Donnelly (sub McDonald 80min), Norris, Dack, Dickenson, Wright, Oshilaja. Unused subs: Morris, Ehmer, Williamson, McGlashan.
Half-time: Peterborough United 0-0 Gillingham
Attendance: 5,083 (728 Gillingham fans)
Full-time: Peterborough United 1-1 Gillingham