A poor weaver rescues a golden silkworm on a rainy night. In her entire life she spits only one golden thread, woven into miraculous brocade to pay off crushing debts, with a promise that once the debt is cleared he will send her back to the old mulberry forest. But when wealth comes before him, time and again he breaks his promise and locks her away, wanting to force her to spit a second one. The spirit silkworm is snatched by villains and forced to spit silk, and his family fortunes decline accordingly. When he exhausts all his family possessions to redeem her does he realize, that the non-existent second thread he locked away was always his own true heart.