They argued over Cains lack of support towards Holly, and as usual Cain storms off to sulk. Feeling sorry for himself he ends up drinking with Charity and later ends up kissing her.
The next day after talking it over with Chas, she advises her brother to go home to his wife. Later Cain and Moira make up, but feeling guilty over the kiss Cain tells Moira what happened between him & Charity. Moira is livid and kicks Cain out. It spirals over the next month with Charity's interference and Cains jealousy over James.
Total BS story line for them to end their relationship over a kiss. After everything they had been through James/DNA/Adams real father and kisses Chrissie/Pete.
Opps I forgot about Moira lying to Cain about her HIV scare.