Collector

Marked One investigates the hints dropped by the mysterious Collector, who disappeared in the Zone recently. This is the first quest in the chain.
== Walkthrough ==
The quest line is started by talking to Sidorovich after saving Nimble, choosing "Why are you so joyful?" in the dialogue. This spawns the first Collector's note, located in a ruined house across the campfire in the Rookie village, under the rusty metal sheet. This is the first hint that will lead you through the stash chain. 
File:Сталкер ОП 2.1 Записка Коллекционера и первый тайник|0:50 for note location
== Notes ==
* Collector is a major "low-intensity" questline that leads you through most NS locations as they unlock. It's strongly advised to follow it as soon as possible, because it offers great rewards, even by the late game standards. However, the stashes are incredibly hard to find, let alone access. Many of them require physics exploits to get to, or/and are located outside of map boundaries. You're expected to watch video guides for most of them.
* This quest is not marked in your PDA and the stages don't have any canonical name. Instead, you can follow the breadcrumb trail of cryptic notes that are contained in every stash.
* Typically, each stash spawns in one of the several predefined places.
* You could use the "Collector stashes" cheat in the settings menu and reload to where you did not have the cheat enabled. Even then, it is advised to follow the video guides to get access to the stash. Keep in mind that using any cheats in the options will break the "no-cheating" conduct and you won't get the corresponding achievement at the end of the game.
== Bugs ==
* It's reported at least by one person that notes in stashes could fail to spawn, blocking the entire questline. If you don't want to take the next one in the chain right now (e.g. you don't have the transition), just ensure that you have the note in the current stash, but don't pick it up, leaving it for later.