Complex sentence: Daniel joins the SG-1 team in search of his kidnapped wife (she dies in season 3) and remains part of SG-1 until his ascension at the end of season 5.
Split into simpler sentences: Daniel joins the SG-1 team in search of his kidnapped wife, until she dies in season 3. However, he decides to remain a part of SG-1, and does so until his ascension at the end of season 5.