Recently, theorists have raised concerns that pedagogical content knowledge (PCK) has become "a stale metaphor" that disregards diversity and equity, offers little to help teachers address students' misconceptions, and portrays knowledge as "in the head" versus in practice. We refute these notions using grounded theory to specify ways one 7th-grade science teacher enacted PCK to advance student learning. With the definition of PCK as knowledge at the intersection of content and teaching, we utilised a framework for science PCK to explore instructional decision-making. Interviews conducted over three years revealed specific ways the teacher enacted PCK by designing and delivering instruction built on each of the seven conceptual science PCK components. The teacher enacted PCK to plan and deliver instruction that was responsive, adaptive, and considerate of changing needs of students and the changing classroom landscape. She infused PCK into instructional decision-making, instructional interactions, and mentoring of a student teacher, modelling the translation of educational theory into practice and habits of mind necessary for expert teaching. This enactment actively refutes Settlage's critiques, and depicts PCK as a vibrant and effective stance for teaching that enhances learning.