This case study focuses on 11 individual teachers who participate in three distinct professional learning communities (PLCs) within one school. A PLC is "a group of people who take an active, reflective, collaborative, learning-orientated, and growth promoting approach toward the mysteries, problems, and perplexities of teaching and learning" (Mitchell and Sackney 2009, p. 30). Through this study, the practical implementation of a new PLC is explored using the criteria from Mitchell and Sackney (2009) with particular emphasis in this paper on the level of interdependence of teachers in these particular PLCs. There were three groupings of teachers who participated in the separate PLC meetings: Kindergarten/Grade One teachers, Grade Two/Three teachers, and Grade Four/Five teachers. All of the groupings consisted of three to four teachers. Although this study is focused on all of the participants' experiences with participating in a PLC, it is important to note the differences in how each grouping conducted their professional development. Each group organized their PLC in slightly different ways, depending on the needs of the group and the subjects within the group. As a result of the case-study approach, which allowed for a wide range of data to emerge through the open-ended interviews, a point of interest--vulnerability--emerged from the data analysis. The interview questions were open-ended and allowed the subjects to openly share information that was relevant to their experience, which in the case of one group led to the emergence of the concept of vulnerability. The teachers who showed vulnerability and became dependent on the other group members allowed for greater improvement of practice to be observed. The other two PLC groupings did not obtain a level of interdependence, but rather focused on sharing insights and resources. There was no vulnerability connected with the Grade Two/Three and Grade Four/Five PLC participants. The noticeable point of interest was the relationship that developed among the subjects of the grouping that showed interdependence, which was complex rather than superficial. The community that developed within the PLC was a group of individuals who were bonded together by natural will and who together enhanced the overall strength of the PLC by creating a set of shared ideas and ideals.