Complex sentence: At the end of season three, Nick's Grimm powers are removed by Adalind as a result of sleeping with her when she disguised herself as Juliette, but he regains his powers in "Highway Of Tears".
Split into simpler sentences: At the end of season three, Nick's Grimm powers are removed by Adalind as a result of sleeping with her--she had disguised herself as Juliette. He regains his powers in "Highway Of Tears".