Continuity mistake: At the fair when Isabelle goes to give Suzanna the baby, she actually hands it to her in one shot, but in the next (a split second) Suzanne shows no sign as if the baby ever left Isabelle's hand. (01:38:24)
Continuity mistake: Just after Samuel and Alfred say that they are going to enlist, Samuel has a weird looking face and notice Alfreds shoulder right behind him, then Susanna takes a few steps up the stairs very sad and Samuel walks a couple of meters towards her and then she leaves and then it switches to Samuel with the same funny looking face and Alfred is again right behind him. (00:24:20)
Continuity mistake: After Susannah's arrival at the ranch she takes a walk around. When she passes by the Deckers the sun has already set. In the next shot, when she talks to Isabell Two, the sun is shining again. (00:12:40)
Continuity mistake: When Tristen arrives home after being gone for many years - he sits with his father, Col. William. The Colonel has a chalk board around his neck and he writes, "Am Happy." Tristen replies, "Me too." The next scene shows the "Am Happy" chalk board again, but the printing is different from when the Colonel wrote on it in the previous scene. (01:22:00)
Continuity mistake: In the farewell scene when the boys are leaving to enlist in Canada, we first get to see Samuel hugging Decker and Alfred hugging. Behind Alfred's neck we get a glimpse of Isabel Two's head as she is jumping up. This can only be Isabel Two approaching Tristan. In the next shot we get to see this again as the camera focus on Isabel Two running towards Tristan and jumping up into his arms. (00:27:25)
Continuity mistake: When the young Tristan is wounded by the bear, his arm gets hurt and the sleeve of his shirt torn. When his father treats a few seconds later the sleeve is intact again and the wound seems to be on his chest. (00:05:50)
Continuity mistake: When Tristan, Alfred and Suzanna run into each other at the fair, the baby is asleep in one shot, then awake in the next and back asleep once again in the next shot.
Continuity mistake: During the war scene, when Samuel gets grazed by a bullet and Tristan covers him for protection, Samuel's hat falls off. The hat reappears, then disappears again. (00:35:57)
Continuity mistake: When Tristin, his father, the Indian, and another man are in a bar trying to get four drinks after they were going to hunt the big grizzly bear, the bartender will not give them four drinks because of the Indian. Watch as Anthony Hopkins tries to stop Brad Pitt and as they keep looking back at the bartender and the other people. If you watch the beer with no foam, it is a little less than full and then it becomes full again. The foam also changes a little. (01:06:08)
Continuity mistake: When Colonel Ludlow and Susannah are eating dinner alone and hear the Decker's laughter from the room next door, they decide to join them. Susannah grabs her plate and her glass, and the Colonel his plate and the wine decanter. When entering the Decker's kitchen, there is nothing but their own utensils, plates and glasses on the table. If Pet brought more mugs and maybe also glasses to the table, she must have been very quick since it takes seven seconds from the last shot of her sitting at the table to Susannah starts pouring wine into a black mug, and gives it to Pet. Even if we only see Susannah pouring wine into one glass in addition to the mug, there are two kitchen glasses on the table filled with wine. When they raise their glasses there is no longer any glass at Pet's place, neither at Decker's. Pet must have given her glass away to the Colonel which doesn't make sense since he left his own almost full wine glass at the dining room. The amount of wine in the Colonel's new glass also varies from shot to shot measured by the decoration. (00:31:20)
Continuity mistake: The bear strikes his left paw at Young Tristan, and he stabs his knife in the paw, but when the bear leaves, he limps on the right front leg. (This is also mentioned on the production designers' commentary track.). (00:05:20)
Continuity mistake: Tristan finds a calf with its legs caught in barbed wire. In the next shot, when Tristan gets down on his knees to free it, its head is also totally entangled. (01:00:15)
Continuity mistake: In the liquor storage Tristan cuts the other guy on the cheek, and he starts bleeding immediately. This scene is intercut with a scene where Susannah cuts off a lock of her hair. When we return to the storage, the guy takes his hand to the cheek, but now there is much less blood than it was only a couple of seconds earlier, and it has not been wiped off. (01:50:35)
Continuity mistake: Susannah visits Tristan in prison. Whenever the camera is on her her face is touching the bars and Tristan's is a bit away, and vice versa. (01:43:40)
Continuity mistake: When young Tristan gets attacked by the bear he looks for cover behind a huge tree. In the fight he cuts off one of the bear's claws which falls to the ground. When his father, brother, and One Stab come to help him Old Stab finds the claw on the opposite side of the tree. (00:05:55)
Continuity mistake: In the end when they have killed the bad guys you can see the indian singing and dancing over them with a knife and he throws his hat off and it lands on the ground at the car but then there is a wide shot off the whole scenario and the hat is gone. (02:00:30)
Continuity mistake: When Susannah visits Tristan in the prison, she turns her head away as he says "Go home to Alfred", but in the next shot she is looking at Tristan again. (01:45:35)
Continuity mistake: When the barkeeper refuses to serve One Stab beer he flaunts his club and puts it on the counter, with the handle towards him. When Tristan picks it up to hit him the club is turned by 180 degrees. (01:04:05)
Continuity mistake: When Alfred confronts Tristan on the porch, the morning after Tristan has done the deed with Susannah, the buttoning of Alfred's shirt becomes reversed, then changes back again.
Continuity mistake: The headstone on Samuel's "heart grave" had writing in the cross bar ("We will not see him, but we shall join him"), as well as his name below followed by "born" and "died" dates. The next three times the grave marker was shown (from a distance), only "Samuel Ludlow" could be seen etched on it. (00:49:47 - 00:54:54)
Answer: There's nothing to tell us who the listener is. Your theory that it's probably a family member seems entirely reasonable, but there's nothing in the film that would allow the identity of the listener to be narrowed down any further than that.
Tailkinker ★