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The comprehension of magnetically-related phenomena occurring in stellar atmospheres is one of the long-standing issues of astrophysics. The solar corona has always been the starting point to understand coronal physics, because the high spatial structuring of coronal plasmas complicate stellar observations. Stars however show activity levels up to 10^4 times higher than the Sun, and it is not clear how the different magnetic phenomena scale with the activity level. Therefore, direct observations of the different magnetic phenomena in active stars are crucial. However, many of them, among which are coronal mass ejections (CME), remain observationally unexplored. By performing time-resolved X-ray spectroscopy of a stellar flare, we present here the direct and unambiguous evidence of upward and downward motions of plasma within the flaring loop, and, most notably, also of the subsequent CME. The observed motions within the flaring loop neatly agree with hydrodynamic (HD) model predictions, indicating that the standard flare model holds also for flares 10^4 times more energetic than the most intense solar ones. This first direct and clear observation of a stellar CME allows us to infer its mass and kinetic energy. These findings provide crucial clues in the extrapolation of the solar case to higher activity levels, indicating that, in active stars, the kinetic energy loss due to mass expulsion appears considerably less effective.