Complex sentence: Before speaking to the captain, Carson sneaks down the freight deck and removes two explosives and a detonator concealed in David's casket, then goes to the Avionics Section where Julia is sleeping (presumably drugged).
Split into simpler sentences: Before speaking to the captain, Carson sneaks down the freight deck and removes two explosives and a detonator concealed in David's casket. He then goes to the Avionics Section where Julia is sleeping (presumably drugged).