Silent Friend tells three separate stories, all set in different periods across more than a century, but rooted in the same location: the University of Marburg in Germany. First, we meet a neuroscientist named Tony, played by the Hong Kong star Tony Leung Chiu-wai, who's visiting the school as a guest researcher. It's 2020, and when COVID-19 hits, Tony is left stranded on a near-empty campus. Bored and lonely, he stumbles on some online videos featuring a French botanist, Alice, played by Lea Seydoux, and is captivated by her theory that plants have a highly developed consciousness.