The Poison Street Treasure Hunt in Red Dead Redemption 2 is a very rich secondary quest as it allows the player to find a loot worth $ 2,000. To start this quest you have to kill Flaco Hernandez hiding in the Cairine Lake hut. Once Flaco is dead, look in his cabin to find the map.
Once you have taken the map, examine it. You will see that the drawing depicts rocks that resemble a face. This place is called Face Rock and you can find it west of Ringneck Creek. In this area there is a hollow tree, look inside and you will find a second map.
Looking at this map, the drawing is reminiscent of a snake. This place is not marked on the map with a name, but it is a mound located west of Van Horn at the top of a steep hill. Once arrived break the stones that look like eggs to find the third and last map
The third map shows a waterfall. You will then have to head to Elysian Pool to the north west of Van Horn. It is not very far from where you are and you can also fish.
Walk to the waterfall to find a secret passage. Remember to turn on the lantern or you will not see anything! Climb over the first ledge and once you descend down the steep descent, look for another steep path to the right. If you find yourself in an illuminated place, you’ve got the wrong way, come back and do it again.
You will come to a small triangular entrance of the tunnel and you will have to crouch to cross it. At the bifurcation take the path on the right. Once inside the room, get up and look to the left: you will see a ledge on which you will have to jump. Go up one last ledge and you will find 4 gold bars worth $ 500 each.
To get out of the cave you will have to go back to the road fork and this time go left. Or if you should die know that you will return to the beginning of the cave.