Watch Critical (UK) Online Free at CouchTuner. Critical is a 13-part series set in a state-of-the-art Major Trauma Centre, a unit which treats only the most gravely ill or seriously injured. Whether that patient lives or dies is determined by knife-edge decisions and procedures, but can the diverse team of medical professionals knit together and rise to the challenge? Our team hold a life in their hands but in every case they face the agonisingly real fear that it could slip through their fingers. (Source: Sky.com | Your Home for the Latest Sky News, Sports & Entert)