An Appointed Time

 is a mission in Red Dead Redemption.

Story
The Mexican army has killed the rebels in Escalera and caught Abraham Reyes. John Marston arrives to see the citizens fighting the army, and eventually finds a tied-up Reyes, about to get executed. Luisa Fortuna tries to save Reyes, only to get shot, and Marston avenges her by killing two of the guards watching over Reyes. The remaining guard, Raul Zubieta challenges Marston to a duel.

Walkthrough
After winning the duel, cut Reyes loose and head up to the prison. Three Federales will come running out of the door. After killing them, enter the jail and release the prisoners by shooting the locks.

Run back to Reyes to help him during the assault on the hill. There will be multiple enemies and you will be without cover at first. Make your way to the sandbags and take cover behind them. Once you've taken out all the soldiers, follow Reyes to the top, and man the gatling gun.

The rebels will use explosives to open the door. Turn the gun to face the gates, and shoot the TNT. Once the TNT explodes, keep shooting as there will be soldiers on the other side of the gates. After killing them all, move up and into the fort. There will be more soldiers once you get inside, so take cover behind one of the sandbags.

Reyes will tell you to protect the gates, and make sure none of the soldiers that are now coming up the hill enters the fort. You can man the gatling gun, but you might get killed as there's little protection while you're standing there. Take cover behind the sandbags either inside or outside the fort, and kill the soldiers as they approach.

Once you've taken care of the incoming forces, move back into the fort and join up with Reyes. As Reyes' rebels breach through the door, Allende will be fleeing in a stagecoach with Bill Williamson. Head down the stairs behind the house and kill the three soldies still left behind. Get a horse and follow Williamson and Allende.

There are two guards on horses behind the cart, as well as the guard on the gatling gun. Take them all out before killing the guard riding shotgun, as he'll also be firing at you. Riding sideways will make it harder for the gatling to kill you. Either shoot all the horses to make the cart stop or, even simpler, just kill the driver with a well aimed rifle headshot to make the wagon slow to a stop.

Once the cart has stopped, Allende will try to buy his freedom by handing over Williamson. John can then shoot both of the men, or just shoot Williamson or Allende. If Williamson is shot, Reyes will shoot Allende. If John shoots Allende, Bill will stand up, pretending to surrender. He will then take Allende's gun, and try to shoot the two. You can shoot him, or Reyes can if you are not quick enough.

Reyes will invite you on, but Marston turns it down as he has to get to Blackwater.

Bugs
After the player kills Williamson, the Colonel will run away and the player along with Reyes will not be able to move. Marston will remain stationary as if the player had still not killed Williamson. Use a Fire Bottle to assault Reyes, thus allowing a reset at the previous checkpoint.

Also you could try pressing the start button a couple times to initiate the cutscene. When the mission is started it may skip the introductory cutscene and start with the duel with Zubieta.