At the center of the Milky Way, stars orbit something invisible at speeds that make no sense unless an enormous mass is hiding there. The film traces how astronomers built the case for a supermassive black hole, starting with Karl Jansky, who in the 1930s picked up radio static from the galaxy's core while working for Bell Telephone. Decades later Eric Becklin helped develop infrared instruments that could finally see through the dust blocking that region, and in the 1990s two teams, one led by Becklin in Hawaii and another at Germany's Max Planck Institute for Extraterrestrial Physics, tracked individual stars whizzing around the galactic center to measure what was pulling on them. Footage shows the scientists at their telescopes alongside Hubble imagery and animations of the 100,000-light-year-wide galaxy and its roughly 400 billion stars. The film ends with astronomers working toward something no one has yet managed: an actual direct image of a black hole, rather than just the evidence of its gravity.