This adventure was originally made for the BOOT HILL western game, but it can be adapted to any western game campaign.
Promise City, Summer of 1890. The party has just arrived at Promise City, in El Dorado County, Texas, looking for Ben Cartwheel, an old friend of one of the PC's father, and rancher of Promise City. When they get into the town, they see a man dressed in black, with milky white skin, harassing a young lady in her mid-twenties. The party should confront the man, who leaves, but not before saying the PCs will pay for this (There should be no fight, though; we'll need this character for later).
The woman is none other than Elizabeth Cartwheel, Ben's daughter. She takes the party to the Cartwheel ranch, a few miles out of town, where they meet Ben. He explains that the man in black name is Montgomery, and he is Mr. G's right hand. Mr. G is a mysterious and prominent rancher in Promise City, and he "owns the town". He seldom leaves his ranch, The G ranch, and is rarely seen. Ben also tells the party about the news of the last two days, mainly, the disappearance of the town judge, Judge Parson, and also about the kidnapping of the Indian Chief Sitting Bear, from the Indian reservation to the north of El Dorado County.
The party will probably accept Ben's invitations and stay for the night. Next day, they will go to town, and, quite by chance, they will stumble upon Judge Parson's wagon, a few hundred yards from the road. Next to it is Parson's body, shot. Examination of the wagon shows that two people were riding on it, one of them the judge. Marks of horses are seen around the wagon. A few feet from it, the party finds an Indian feather, the type of feather worn by Indian chiefs. And they find a small cigar stub.
If the party informs the sheriff, he will say he'll conduct an investigation, but will be suspiciously uninterested. If the party searches the Judge's office (inside the Promise City Court Room), they will find a clipping from an old newspaper quoting some words from chief Sitting Bear, which are underlined: "... white men have arrived here, sick and bleeding, and we have done for them what we could, but they died here, sharing their last secrets with me...". They also find a map, with a red line connecting Promise City with the reservation, and a name: Richard Flynn.
What's going on:
In the summer of 1880 Richard Flynn, a known thief and outlaw, robbed the Promise City branch of the First National Bank. At the moment the bank vault was holding an important shipping of money coming from California, as well as a number of valuables, the most important of which was a golden necklace speckled with precious stones, the Isabel Piece. The Isabel Piece, an invaluable work of art, originally part of queen Isabel of Spain's personal jewellery, made expressly on the fifteenth century, and supposedly stolen from the Royal Vault in 1624, had been found by chance among the ruins of an old Mexican town in the middle of California. Now, while the Spanish Crown, the Government of Mexico, and the United States waged diplomatic wars to keep control of the newly found necklace, the necklace itself was being transported to the East coast to be displayed in a museum. During the Piece's two-day stay at Promise City, the outlaw Flynn and the two members of his band somehow slipped into the bank and parted, taking almost all of the money and, of course, the Isabel Piece.
During their escape, Flynn and one of his henchmen were wounded. While under subsequent pursuit by the regular Army division that was supposed to have kept the money safe, Flynn divided his band, sending the henchman that hadn't been wounded in a different direction, to throw off the pursuit. This ploy worked to a great extent; when the Army finally captured the diverting outlaw, Flynn and his remaining man had a good four hours advantage. The Army threw itself again on pursuit. Many hours later, when it was obvious for Flynn that he was going to be captured, he and his underling hid the booty somewhere along the road. Having ridden themselves of this bulky weight, they were able to escape and where never seen again.
The captured outlaw, the one who had been sent as a diversion, was put on trial, presided by Judge Parson. Parson was not an honest person, and he saw this as the chance to get his hands on the booty and disappear. The problem was, he had to find out where the money was hidden. To this end he interrogated the outlaw, who didn't know where the booty was, but said Flynn's plan was to lay low in the Indian reservation for a while. Parson conveniently kept this information a secret. The outlaw was finally found guilty of robbery and hanged, although the money was never found.
Ten years go by. In 1890, Judge Parson finds a newspaper article written by a bold young reporter who managed to get inside the Indian reservation and interview Chief Sitting Bear. One particular sentence in the article struck Parson: "... white men have arrived here, sick and bleeding, and we have done for them what we could, but they died here, sharing their last secrets with me...".
Convinced that those words meant that Chief Sitting Bear had a clue to Flynn's final destiny and to the location of the treasure, Parson went to the Indian reservation pretending to be a friendly reporter, and interviewed the Chief about the secrets whispered by those white men. Confronted by the Chief's refusal to disclose the dead's secrets, and already without doubt that those "white men" had been Flynn and his henchman, because of the similitude in the dates, Parson dropped the pretence and kidnapped Chief Sitting Bear, taking him, bound and gagged, back to Promise City.
What Parson didn't know is that for the last ten years he had been closely watched by Mr. G. Mr. G, being wealthy, and also being a jewellery admirer, had secretly hired Flynn to sneak into the bank and steal the Isabel Piece for him. The plan went wrong when Flynn, consumed by greed, decided to take not only the Piece, but also the money, and to doublecross Mr. G. After Flynn's escape and disappearance, the location of the treasure was as much a mystery to Mr. G as it was to Parson. However, Mr. G was convinced that Parson knew something important, and kept a watch on him. That precaution finally paid off.
While returning from the Indian reservation with Chief Sitting Bear, Parson was ambushed by Montgomery and murdered. Chief Sitting Bear was then taken to the G Ranch, where he was going to be interrogated.
Sooner or later the party will start investigating on its own (you should try to push them a bit). They can ask Ben Cartwheel about who Richard Flynn is, or they can go to the Promise City Times newspaper (the "newspaper" is published weekly and is about two pages long). Anyway, they should easily find out about the Isabel Piece robbery and the mystery of the Flynn treasure. The cigar stub should point to Montgomery, who usually smokes expensive cigars (you can change this clue for something more subtle). Of course, if Montgomery is involved, then Mr. G also is. That would explain why the sheriff is so uninterested in the case.
After one or two encounters with Mr. G's men (who by now have figured that the party is meddling around), the party should be ready to sneak into the G ranch (a big complex surrounded by a wooden fence and guarded by G's men) and save chief Sitting Bear. (the rescue should be where lots of the action will go).
After being saved, the chief tells the party that Flynn was really with him ten years ago, and he mentioned that "some important Promise City rancher" had hired him to steal the Piece, and that he had doublecrossed this rancher. Flynn also told the chief the location of the treasure, and he tells the players about it. (you should make the location of the treasure a cryptic message which the Indians would not be unable to understand because they don't know the proper names; for example "three gun-lengths north of the division of the river of the Griffin", where Griffin is the name of a small town; otherwise, you will have to explain WHY the Indians haven't dug the treasure by themselves!)
The party travels to the cave, possibly having one or two encounters on the way. There are several possibilities here: