The paper presents a detailed study of a radio flare in the Seyfert I galaxy III Zw 2, observed with the VLA and VLBA. The flare, which began in 1996, showed extreme variability in radio wavelengths, with a 20-fold increase in flux density within four years. The observations revealed a phase where the jet was frustrated, without expansion or spectral evolution, followed by a phase where the jet expanded with apparent superluminal motion and strong spectral evolution. These results confirm synchrotron theory and equipartition for jets. The source, III Zw 2, is a core-dominated flat-spectrum AGN with a weak extended structure. It is located in a spiral galaxy and has a compact core and a flat, variable spectrum. The source has shown variability in radio, optical, and X-ray wavelengths. VLBI observations showed a high-brightness temperature unresolved core and, in later observations, a resolved structure. The source is a candidate for detecting apparent superluminal motion, which is crucial for testing the relativistic jet hypothesis. The VLA and VLBA observations revealed the structural evolution of the jet. The source showed a dramatic change in the spectrum after November 1998, with the peak frequency dropping to 10 GHz. The spectral evolution was modeled with a broken power-law, showing a change in the spectral index. The structural evolution was also observed, with the separation of the outer components increasing from ~76 μas to ~245 μas, corresponding to a source size of ~0.11 pc to ~0.37 pc. The results show that the jet underwent a phase of expansion and that the spectral and structural evolution are closely linked, indicating a real physical expansion. The findings support the hypothesis that radio-weak and radio-loud quasars can have similar central engines. The study also suggests that the jet interacts with the interstellar medium, with the source being optically thick at 15 GHz and optically thin at 43 GHz. The results are consistent with a model of synchrotron self-absorption and the evolution of the jet in a Seyfert galaxy. The study highlights the importance of multi-frequency observations for understanding the nature of jets in active galactic nuclei.The paper presents a detailed study of a radio flare in the Seyfert I galaxy III Zw 2, observed with the VLA and VLBA. The flare, which began in 1996, showed extreme variability in radio wavelengths, with a 20-fold increase in flux density within four years. The observations revealed a phase where the jet was frustrated, without expansion or spectral evolution, followed by a phase where the jet expanded with apparent superluminal motion and strong spectral evolution. These results confirm synchrotron theory and equipartition for jets. The source, III Zw 2, is a core-dominated flat-spectrum AGN with a weak extended structure. It is located in a spiral galaxy and has a compact core and a flat, variable spectrum. The source has shown variability in radio, optical, and X-ray wavelengths. VLBI observations showed a high-brightness temperature unresolved core and, in later observations, a resolved structure. The source is a candidate for detecting apparent superluminal motion, which is crucial for testing the relativistic jet hypothesis. The VLA and VLBA observations revealed the structural evolution of the jet. The source showed a dramatic change in the spectrum after November 1998, with the peak frequency dropping to 10 GHz. The spectral evolution was modeled with a broken power-law, showing a change in the spectral index. The structural evolution was also observed, with the separation of the outer components increasing from ~76 μas to ~245 μas, corresponding to a source size of ~0.11 pc to ~0.37 pc. The results show that the jet underwent a phase of expansion and that the spectral and structural evolution are closely linked, indicating a real physical expansion. The findings support the hypothesis that radio-weak and radio-loud quasars can have similar central engines. The study also suggests that the jet interacts with the interstellar medium, with the source being optically thick at 15 GHz and optically thin at 43 GHz. The results are consistent with a model of synchrotron self-absorption and the evolution of the jet in a Seyfert galaxy. The study highlights the importance of multi-frequency observations for understanding the nature of jets in active galactic nuclei.