The contestants are tasked with cooking a three-course fish lunch for some of the country's biggest fish experts. Starting at 4am at Billingsgate Fish Market, they must first source their ingredients before moving on to Fishmongers' Hall, the prestigious headquarters of the Fishmongers' Company, where they take full control of the kitchens. John Torode oversees the kitchen as the amateurs face a high-pressure lunchtime service. The contestants must each serve one dish of their own creation on the specially designed menu, and the two chefs who cook the most popular dishes will be exempt from the next cook-off. Back at the MasterChef kitchen, the MasterChef market reopens as the five chefs cook against each other in a bid to stay in the competition, and this time there is no meat or fish. They have one hour and fifteen minutes to create one dish to keep themselves in the competition.

It is the final week of MasterChef 2017, and the remaining five amateur cooks travel to Winfield House, the official residence of the American ambassador to the United Kingdom. They have the immense task of cooking for him and his five guests, who include author and journalist Rachel Johnson, Wikipedia founder Jimmy Wales and Jeremy King, creator of iconic restaurants The Ivy and The Wolseley. The dinner is overseen by Paul Ainsworth. He has designed a five-course menu for the guests with an American theme, and with just four hours to replicate his complex dishes, the amateurs are challenged like never before. Back at the MasterChef kitchen, the finalists are then challenged to demonstrate everything they've learnt and create a dish inspired by something personal in their lives that shows imagination, flair and creativity. Who can make it through to the final four and keep their dream alive of winning MasterChef 2017?