Emmerdale spoilers follow.

Emmerdale launches Billy and Dawn Fletcher’s huge new storyline on Wednesday evening (May 1), as they find a mysterious bruise on their baby son Evan.

The couple are confused and concerned when they spot the bruise, which seems to be unconnected to their young son’s recent fall.

Evan was checked over at the hospital last week after suffering a nasty fall when Billy turned his back on him for a moment.

Dawn insists that the new bruise has appeared more recently, which she doesn’t understand, as Evan hasn’t been left unattended since returning from hospital.

When Billy and Dawn raise the alarm with local doctor Liam Cavanagh, they list some other symptoms that Evan is experiencing.

Liam takes the situation seriously and urges the couple to take Evan to A&E immediately.

Billy and Dawn are initially worried that they’ll be wrongly accused of hurting Evan, considering the previous accident and Dawn’s troubled history with social services.

Blood tests are carried out, and the paediatrician tells Billy and Dawn that Evan is very unwell.

The couple are informed that their son will need an urgent bone marrow biopsy, as he has low haemoglobin and platelet levels.

Emmerdale bosses recently confirmed that Evan will be diagnosed with leukaemia this week, marking the beginning of a long-running story for Billy and Dawn.

Show producer Laura Shaw told Digital Spy last month: “We’re going to see their world totally rocked when, almost out of nowhere, Evan is diagnosed with acute lymphoblastic leukaemia (ALL).

“ALL is one of the most common childhood leukaemias. I think there’s 650 children and young adults diagnosed with that every year in the UK.