Complex sentence: When Logan feels conflicted about whether to testify about his knowledge of Marino's complicity in those crimes, he turns to advice from Cragen, who comforts Logan and ultimately helps convince Logan not to commit perjury by lying about Marino.
Split into simpler sentences: When Logan feels conflicted about whether to testify about his knowledge of Marino's complicity in those crimes, he turns to Cragen for advice. Cragen comforts Logan and ultimately helps convince him not to commit perjury by lying about Marino.