Mr. Isaac Atkinson, the owner of The Star of Sierra Leone, a 968-carat diamond, takes it with him onto The Contessa, an elegant new cruise ship bound for West Africa. The Star invites many problems and puts the little jeweler in some very serious situations. Meanwhile, the inhabitants of Sierra Leone are facing Ebola, they die by the dozens every day. The World Health Organization team boards the Contessa to carry the vaccine to the population, which will bring this unprecedented epidemic to its knees. The ship's physician, Dr. Alan Mayhew, and his nurses assist the WHO team in what proves to be one of their most difficult missions yet.