As announced in March, a special bonus edition of the show due to air at the end of this month will see Sean head to London to spend time with his son Dylan.
In an interview with All About Soap, Cotton confirmed that Sean discovers all is not well between Dylan's mother Violet Wilson (Jenny Platt) and her partner Jamie Baldwin (Rupert Hill) soon after he arrives at their home.
A further twist sees Sean's reunion with ex-boyfriend Marcus Dent (Charlie Condou) take place at Violet's as Marcus is also visiting the couple.
Cotton explained: "Things aren't great between [Violet] and Jamie, and Sean walks into a big old domestic. He heads to the kitchen to see Dylan while they argue and he's stunned to see his ex-boyfriend Marcus feeding Dylan his meal!
"Marcus has kept in touch with Violet and Jamie and visits every now and again. Marcus joins Sean and Dylan for their day doing London tourist stuff. He was very important to Sean and that hasn't changed."
The actor added that Sean later leaves London on a sour note following a row with Violet.
Asked whether it is difficult for Sean to leave Dylan behind, he replied: "Yes, very difficult and all goes a bit wrong at the end. Violet says some quite nasty things to Sean and he's left wondering if he'll ever see Dylan again."
Earlier this year, reports suggested that Sean would soon become a hands-on father at last, raising Dylan in Weatherfield with Marcus.
Corrie's Easter special, which also features a one-off return from Bruno Langley as Todd Grimshaw, airs on Sunday, April 24.
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