Freddie was conceived in late 2003 when his mother, Little Mo Mitchell, was raped by her friend, Graham Foster. Her refusal to abort the child caused the break-up of her marriage to Billy Mitchell. Mo stayed with her sister, Belinda Peacock, where she gave birth to Freddie. In November 2004, after Graham is sentenced to eight years imprisonment, Little Mo and Billy make another attempt at their marriage, but they separate again after Billy admits that he struggles to accept Freddie. Freddie then lives at the Slater household with Little Mo, his great-grandmother Big Mo, his grandfather Charlie and second cousin Stacey.
In February and March 2006, Freddie causes his mother much stress by crying a lot. He takes a trip to the park with his mother, Jane Collins and Bobby Beale, where Bobby pokes him in the forehead with a stick. Freddie has to go to hospital but was thankfully is okay. However, the incident results in a visit from a health visitor. Mo thinks that the health visitor is accusing her of abusing Freddie and becomes angry and hostile. Mo struggles to cope with her young son as when he is teething he often cries.
In May 2006, Freddie goes to hospital seriously ill with bleeding on the brain. A few days before the hospital admission, Mo admits to her boyfriend Oliver Cousins, who is also a GP, that she sometimes gets very irritated with Freddie when he cries. When Oliver hears that Freddie's injury must have been caused by shaking or rough handling, he admits what Mo has told him to a paediatrician, Briony Campbell, at the hospital. While the hospital believes that Mo may have shaken her son, Mo suspects that ten-year-old Ben Mitchell may have hurt him in some way as they were left unsupervised together just before the incident. Mo confronts Ben and shakes him in irritation when he tries to run away. After extensive tests at the hospital, it is discovered that Freddie has a temporary low platelet count, due to an infection, meaning that any minor injury could hurt him badly, as his blood isn't clotting properly. Mo is no longer suspected of hurting her son. Freddie leaves Walford on 26 May 2006 with his mother who wants to start a new life in Barnstaple, Devon.