[en] Changes in the fibril geometry associated with a subflare are tracked in detail in both time and space. The fibril morphology at the location of the subflare is a spiral configuration surrounding a sunspot. Despite the rotation of this sunspot, which tends to tighten the spiral structure, a relaxation toward a more nearly radial structure is associated with the occurrence of the subflare. The relaxation is confined to those fibrils which connect the poles of the optical flare emission, and in addition, tends to reflect the different time evolutions of different parts of the subflare. Comparison of the changes in the fibril geometry with the soft X-ray burst indicates that the reorganization of the fibril structures lags the energy release in the subflare by more than one hour. (Auth.)