Complex sentence: On the advice of the archeologist Gromozeka they look for with the help of doctor Verkhovtsev, the director of the museum of Two Captains, but the doctor behaves suspiciously: doesn't show them diaries of captains and starts spying on the expedition.
Split into simpler sentences: On the advice of the archaeologist Gromozeka, they turn to Doctor Verkhovtsev, the director of the Museum of Two Captains, for help. But the doctor behaves suspiciously: he refuses to show them the Captains' diaries and starts spying on the expedition.