Jonathan Howard is building a nuclear fusion reactor in the spare room of his South London flat, using scrap parts and components bought off online marketplaces rather than a lab budget. The film follows his attempt to replicate, on a hobbyist's income, the process that powers the sun: heating plasma past the point where atomic nuclei fuse and release energy. Setbacks pile up alongside the wiring and vacuum chambers, from failed experimental runs to the ordinary problem of paying for parts, and the film stays close to those daily frustrations rather than treating fusion as an abstract goal. Physicists interviewed along the way describe the challenge in blunt terms, comparing controlled fusion to putting the sun in a box, and explain why so many well-funded institutions have spent decades chasing the same result. Howard's project sits against that backdrop as a test of what a single determined amateur can actually achieve with a soldering iron and secondhand components, and the film treats his persistence as the real subject, whether or not the reactor ever works.