I Promise

Pre-Avengers. First story of my Avengers arc. Loki has fallen ill and Thor refuses to leave his side. Worried about his little brother he makes a promise to him, but finds that in the future when Loki truly needs him, he fails and Loki falls off the Bifrost. Thor's regret after Loki's "death." Takes place from the end of Thor (2011) to the Avengers (2012) movie.