The Ghost (2008)

In Moscow, Anton is out of ideas for his "Ghost" novels about a hit man, based on old news accounts. At a book signing, a man buys Anton's latest; then, on a street below, Anton sees the man murder a witness in an upcoming trial. Days later, the killer chats up Anton at a café, offering ideas for plots. Anton accepts and his writing improves. Meanwhile, he has a troubled relationship with Mika: she's forgiving, but his drinking and late-night writing sessions drive her away. Plus, he spends precious little time with his son, who's in an institution. Slowly, the hit man raises the ante with Anton: how far will a writer go to understand his fictional character?