Jeff Morton was on his way home from Greenwood to his cabin near Dawson with a doll for his poorly little girl Mary when he came across escapee Turrango and his Renegades heading from Christmas Creek toward the nearby little community of Greenwood, Jeff is injured by the gang but manages to get back to Greenwood and warn them. 

Sergeant Preston took charge of the preparation for the siege and little Sonny was upset that Turango would spoil Christmas Eve. Turango backed off but afraid they would be back Sergeant Preston heads back to Dawson to bring reinforcements. On the way to Dawson he goes to get Jeff's children Paul and Mary. So that she will have a present for Christmas he takes the doll for Mary. In his red uniform with the doll Mary thinks that Sergeant Preston is Santa Claus. She is delighted when Preston tells her the story of Christmas. 

Lovely little Christmas episode.