With his fragile relationship with ex-girlfriend Maria showing signs of improvement, Marcus has finally been allowed to visit little Liam, much to a jealous and manipulating Todd's annoyance.
Unaware of the lengths Todd would go to to keep Marcus away from Liam, Marcus is blind to what kind of relationship he has found himself in.
Charlie explained: "I think he feels like he is starting to get back on track now, he's with Todd, he loves Todd, he feels like it's going in the right direction - so he thinks everything is alright.
"He doesn't realise how bad Todd is, I think he wants to see the good in everyone, he always does, so he's not really seeing what other people are seeing, but then love is blind.
"It's really hard for Marcus because the one thing he is really missing about his last relationship, is his relationship with Liam - Maria's little boy - and he really, really misses him and wants to see him all the time and Todd's not really happy with that."
With Marcus wanting to keep the peace, he decides the best thing to do would be to not tell Todd about his access to Liam.
Charlie said: "Marcus is determined to see Liam so he kind of goes behind (Todd's) back a little bit, or just doesn't tell Todd that he is going to meet up with Liam.
"But it all comes out and Todd's fairly upset.
"He gives him a really hard time and it's all a little bit out of proportion. Marcus feels terrible because he is not somebody that lies and Todd just doesn't let him off the hook.
"And he also decides that that is the perfect excuse for him to go off and play around behind Marcus' back."
Marcus is soon hit with the light of realisation when he sees a drunken Todd parading along Coronation Street with another man...
"Todd shows absolutely no remorse at all, he's completely unashamed. Marcus ...sees Todd and this guy Johnny together and sees them kiss and then suddenly it all falls into place.
"Marcus goes absolutely nuts and goes for Todd.
"I think this could definitely be the end of the road for Marcus. He just feels like there's nothing left for him in Coronation Street.
"There's nothing there for him anymore and it's time for him to move on to pastures new."