This paper examines a series of naturally-occurring phone calls between a young child and his grandmother in the child's second language. During these calls, the child's second language production first appears to increase in complexity, but is subsequently abandoned. It is argued that while the acquisition of the second language can be viewed as a product of expert-novice interaction, the subsequent abandonment of the second language can be understood only by examining its role in the larger socio-cultural activity in which the L2 is used.