It’s no coincidence that Christopher Plummer finally won an Oscar acting opposite McGregor or that Nicole Kidman scored her first nomination sharing scenes with him. McGregor is one of those actors who brings out the best in everyone around him. In “The Impossible,” McGregor has never been better as Henry, whose wife, Maria (Naomi Watts), and son Lucas (Tom Holland) are separated from him by the 2004 Indian Ocean tsunami. Searching for his family, McGregor is an open wound of grief but also determination.