In the comedy-drama Mainstream, a young woman finds a path to internet stardom when she starts making videos with a charismatic stranger. Frankie is a young filmmaker living in West Hollywood. Despite dropping out of school to pursue her dreams of making art, she is working a thankless job bartending with her friend Jake and has no clear vision of her goals other than a struggling YouTube channel. One day she encounters Link, an eccentric young man working as a costumed mascot in a mall. When Frankie claims to have been filming a painting behind Link and not Link himself, Link grabs the painting and performs a rambling but passionate monologue urging passersby to pay attention to the art. Frankie records the monologue and uploads it where it quickly becomes her most popular video. Frankie later accidentally re-encounters Link by chance and befriends him. The often-manic Link claims that his parents are dead and that he is firmly anti-establishment and anti-social media.