How to run different time periods simultaneously in your RPG

Skull RPG: Game Masters Tell Your Story

Hey Storytellers,
Today we will talk about how to run a game using two or more different timelines that your players will play through with two or more different sets of characters.
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Kenneth Hite in his Dracula Dossier for Nights Black Agents (https://www.drivethrurpg.com/product/195799/The-Dracula-Dossier-Core-BUNDLE) had a cool concept of playing a game that took place in the late 1800s during the time of the book Dracula from Bram Stoker, 1970's mole hunt spy operation and modern-day spy thriller. The characters could progress from one timeline to the other.
If you are up for it though you could have your characters roll up two sets of characters and have them only play in modern times until they come across a McGuffin (plot device). Then they would pull out their other characters and play out the creation / discovery / theft of the McGuffin.
Remind the players that these flashbacks are not in chronological order. This allows you to do a total party kill (of the old characters) and still keep them around if you want.
Listen to the episode for more ideas.