Jake's Campaign revolves almost entirely on Sherry getting Jake back to America so they can use him to produce a C-virus cure. You see, he's the son of Albert Wesker and has the C-virus antibodies because of it. Problem is, Jake is a heartless ass who cares only about himself, and Neo-Umbrella wants him bad, so they can strengthen the C-virus. Worse, Neo-Umbrella sent out the Ustenak, a Nemesis like creature to apprehend him. Also, Sherry has some sort of healing factor thanks to the G-virus from RE2. She's kinda boring otherwise.
Long story short, Jake lightens up, defeats the Ustenak together with Sherry, and they escape to save the world.
"It is only [in La Mulana] that we entrust our fate." -Japanese indie developer NIGORO on their love of the art.