Location: This mission becomes available after you complete the Accepting the Truth side mission. Wait for an e-mail from Marnie, open it and click on the link contained in it, thanks to which you will visit the www.epsilonprogam.com site again. Select the option of donating $5000 to the cult's account.
NOTE: If you are playing the basic version of the game (no patches installed) you need to mind the fact that there is a serious glitch in the game, which may make you unable to unlock the remaining missions connected with the Epsilonist cult. I recommend that you save the game before you start this mission and save again only after the completion of the ENTIRE mission, i.e. at earliest, after you receive another e-mail message from Marnie (after you steal all five means of transport).
You now need to wait patiently, until near the airport, there appears the cult symbol in the Northern part of the map (to the North of Sandy Shores). (letter E on the world map). After you get there, (the Grapeseed location) have another conversation with Marnie to learn that Marnie desires Michael to acquire four rare car models and one rare motorcycle for her. Wait for an e-main from Marnie which is going to include the names and the pictures of the vehicles in question. The game will not point you to specific places where you can steal the vehicles that the cultists are interested in. Therefore, you will have to find them on your own. Note -detailed information on the available means of transport are contained in the "GTA V - Maps and collectibles" guide.
Pegassi Vacca is a car that you may notice while exploring the Vinewood district. One of such cars is parked in front of the estate in the Eastern part of this district.
Benefactor Surano is a car that you see pretty often in Vinewood, Rockford Hills and the other more luxurious districts of the city.
Declasse Tornado is a car that you can find in many different areas of the game world, e.g. in front of an estate in the central Vinewood and in front of the car garage in the Hawick district.
Enus Super Diamond is a car that you see in Vinewood Rockford hills and the other luxury districts on a regular basis.
Dinka Double-T is a bike that you may notice while exploring Vinewood. One of these is parked behind an estate in the Eastern part of this district.
You need to deliver all of the stolen means of transport to the garage adjacent to one of the estates in the central Vinewood. After you have performed all of the actions, DO NOT SAVE the game and wait for confirmation from Marnie (the above screenshot). The result of this message should be unlocking the next mission automatically.
Rewards for the completion of the mission: none
Requirements for the completion of the mission in 100%: There are no additional requirements for this mission so, it gets completed in 100% automatically.