Complex sentence: Cale also finds a recording by his father in the event that the Drej had gotten to him first and in the event that Cale had arrived at the Titan where the recording urges Cale to finish the job of preserving the human race.
Split into simpler sentences: Cale also finds a recording made by his father in the event that the Drej had gotten to him first and in the event that Cale found the "Titan". The recording urges Cale to finish the job of preserving the human race.