Hearing parents of deaf or partially deaf infants are confronted with the complex question of communication with their child. This question is complicated further by conflicting advice on how to address the child: in spoken language only, in spoken language supported by signs, or in signed language. This paper studies the linguistic environment created by one such mother (language input and parental behavior) and her child's language production longitudinally during the first 2 years of life of the infant to discover possible relationships. The mother-child dyad was observed when the child was 7, 9, 12, 18, and 24 months old. Changes in the mother's approach to communication with her child and their consequent effects on the child's language development will be highlighted. The infant concerned has a hearing loss of more than 90 dB on both ears, which qualified her for cochlear implantation. At the age of 10 months she was implanted on her left side (30/04/2010). Five months later she received a second implant (24/09/2010). By means of several assessments instruments the created linguistic environment, the language development of the infant in question and possible causal relationships were investigated before and after implantation. These instruments include: Pragmatics Profile of Everyday Communication; Profile of Actual Linguistic Skills; video-images of interaction analyzed in ELAN; MacArthur-Bates Communicative Development Inventory for spoken Dutch and Flemish Sign Language (from 9 months onwards). Results for each individual assessment moment are given as well as an overarching interpretation of evolution in the language development. The child seems to be profiting from a bimodal/bilingual approach to communication up to 9 months of age. She is progressing considerably in both spoken Dutch and Flemish Sign Language, with a possible onset of functional code-switch. However, a setback is evidenced in the child's language development, mirrored in a setback in the mother's sensitive behavior as she moves to a more monolingual approach after cochlear implantation. (Contains 7 figures and 11 tables.)