British director Tim Roth heads the jury for this year's "Un Certain Regard" competition, with new work from 17 up-and-coming directors including David Cronenberg's son Brandon, and fellow Canadian Xavier Dolan who is just 23.

"We're going to suffer heartbreaking stories, and happiness and comedy -- and it will be a challenge but it will be a lot of fun, and this is what film does," Roth quipped on stage before the gala screening.

"Mystery" marks Lou's return to official film-making in China after the director received a five-year sanction for his politically-laden 2006 movie "Summer Palace", which screened in Cannes.

He had to shoot under cover for his 2009 "Spring Fever", a steamy gay-themed love triangle that won a Cannes screenplay award, while his "Love and Bruises" was made in France.

"We are happy he is able once more to work as a film-maker at home in China," festival general delegate Thierry Fremaux said as he introduced the director's new film.

Starring Hao Lei and Hao Qin and set in urban China, "Mystery" tells of a young mother who discovers her husband is leading a double life, with dramatic consequences for all involved.

Its critical reception in Cannes was cool however with the Hollywood Reporter summing it up as a "blandly-titled, rain-soaked romantic melodrama... despite two strong performances by the female leads."