Ben Wade (Russell Crowe) is a notorious outlaw who holds up a money train - but then gets busted meeting up with his girl in town a little later.  Dan Evans (Christian Bale) is a poor rancher who decides to take the dangerous job of escorting Wade to the town of Contention to get him onto the 3:10 train to Yuma where he'll be tried and hanged - unless Wade's ruthless gang can catch them first.

So Evans, his son William and Butterfield get Ben Wade to the town on time. They take a time-out in a local hotel and watch the streets waiting for Wade's men to show.  The Railroad Rep brings in help from a few other law enforcers to swell the numbers.

Wade's men, led by the just plan weird Charlie Prince (Ben Foster), ride into town. They ask how he is, throw his bowler hat up to him, and then Charlie puts a price on to the heads of the good guys - promising a wad of cash to any man that guns down Evans and his men.  The new blokes freak out and leave through the front door - just to be shot anyway.

Butterfield strikes a deal with Evans and then leaves with Dan's son out the back. Evans is going to be a hero and stay with the prisoner before somehow taking him to the station.  There's a lot more talking, and basically Evans reveals that he is no hero but wants his son to remember him for one brave deed.  Wade can understand that, so decides to help him, which makes no sense.

Together they walk outside, but gunslingers start firing from all angles.  They both cautiously make their way out through the streets. When the bullets start to get too close to Wade, Charlie starts taking out the greedy townsmen.

After jumping over a few roofs, they make it to the station - and the train is late. Charlie hides out with a load of cattle and the sniper gets into position.  The train shows up.

Dan's son startles the cattle which stampede. The diversion is all they need, and Evans gets Wade onto the train and behind bars.  Suddenly Charlie appears and shoots Evans in the back. Wade shouts to his men to stop, and runs off the train towards them as William runs to comfort his old man.

In anger, and knowing they are all a bit dodgy anyway, he takes Charlie's gun and shoots his men dead -- including his little friend Charlie, who has tears in his eyes as he falls.  Dan dies.  Wade gets back onto the train and behind the bars - but as he said earlier, he had already escaped from the Yuma jail before anyway.  It still doesn't make all that much sense though.
  He whistles and his trusty horse runs alongside the train - but without any means to get on board, plus it probably doesn't have a ticket, it's going to be a long journey to Yuma.