The Expresso Project

"Great. Let's get going. We haven't got much time. We'll meet again tomorrow - same time, same place. And we'll call our plan... what?" "How about 'The Expresso Project'?" says Luigi. 

Today, I'll introduce 'The Expresso Project'.
One day, Gil, Sato, and Jodie are in a  big park in London. Sato is the best friend of Gil and Jodie is Gil's new girlfriend. After that, they go to The Hard Rock Cafe and  have some drinks. When they pay money, Gil finds that his wallet has been stolen. Sato remembers that Nic, a Russian friend of Gil is also in the park so Sato doubt  that Nic is a thief. But Gil doesn't think that.
In the meanwhile, Jodie has a little brother and he is in a children's hospital because he is very well. She wants to help him.
You may think that these two things have little to do with each other. However, actually, these are very closely related.
Who is the thief and what is The Expresso Project? Please imagine this before you read it!