Dylan Keogh returns with a vengeance in ‘The Whistleblower,’ determined to expose Patrick Onley’s true nature. Stevie Nash’s shocking discovery fuels his efforts, while Holby ED faces potential closure. Ngozi Okoye makes a startling confession, and Patrick betrays Siobhan Mckenzie, leaving her vulnerable. Faith Cadogan and Siobhan clash over the whistleblower’s identity, and Cam Micklethwaite battles with his confidence.