She disappeared. Why did she get a lawyer?

In the movie "She Disappeared", He Fei sought a lawyer to prove that Janice Man was a fake wife and thus inherited a huge inheritance. Because He Fei's wife disappeared during the trip, and He Fei found that the so-called "wife" was actually an impostor, and there may even be a behind-the-scenes team manipulating this scam. In order to expose the truth and get legal support, why not seek the help of a lawyer? This is also one of the important plots to promote the development of the plot.