The Pelican's Secret

A murder has been committed overnight on the Pelican’s Grace, and on the thirteenth night no less. Your dear friend Captain Yorshank, who you remember fondly from the good old days, fears for his job upon returning to port. His only hope of salvaging this situation is if he apprehends the murderer before facing his employers. He calls to you, his dear friends, to investigate the scene of the crime and provide him the motive, weapon and opportunity for the murderer to commit the crime.