As Holby City fans will know, Doctor Arthur Digby (Rob Ostlere) discovered that he had cancer when he underwent compatibility tests to see if he could be a donor.
His colleague, transplant coordinator Essie, spotted an irregular-looking mole on Arthur's back, which later was revealed to be cancerous.
However Arthur went on to have the mole removed - and life seemed as if it would return to normal for the Holby favourite.
And, in tonight’s episode, Arthur seems to be on Cloud 9 after he takes a risk and reaps the professional benefits.
But, as the young doctor prepares for his and Morven Shreve (Ellie Fanyinka)’s engagement party, Arthur is soon brought back down to earth in a terrifying way.
Viewers will watch as Arthur begins coughing up blood, before rushing off to search for Dominic (David Ames); he needs his best friend’s help.
Dom is shocked by Arthur’s admission, and soon forgets their earlier fall-out.
In a bid to try and put Arthur at ease, Dom agrees to scan his friend’s lungs - but his face soon falls as he watches the screen.
Unable to hide the emotion in his voice, Dom soon confirms the worst; Arthur has secondary tumours in his lungs; the cancer is back.
Will Arthur be able to fight off the disease for a second time?
This episode of Holby City airs tonight (Tuesday) at 8pm on BBC1.