This paper concludes the Special Issue (SI) 'Probing the Amalgam: the relationship between science teachers' content, pedagogical and pedagogical content knowledge'. We review the five papers (Sorge et al; Gess-Newsome et al; Kind; Pitjeng-Mosabala and Rollnick; and Liepertz and Bronowski) by discussing evidence these present regarding the relationships between content knowledge (CK), pedagogical knowledge (PK) and pedagogical content knowledge (PCK); the development of CK, PK and PCK in novice and experienced secondary science teachers and how CK, PK and/or PCK impact students' learning. In conclusion, we draw these findings together in offering proposals for future research via reconsideration of Shulman's amalgam. This includes post-hoc examination of a PCK model known as 'the Consensus Model' (Gess-Newsome, [2015]. A model of teacher professional knowledge and skill including PCK: Results of the thinking from the PCK Summit. In A. Berry, P. J. Friedrichsen, & J. Loughran (Eds.), "Re-examining Pedagogical Content Knowledge in Science Education" (pp. 28-42). New York, NY: Routledge; Neumann, Kind, & Harms [2018]. Probing the amalgam: The relationship between science teachers' content, pedagogical and pedagogical content knowledge. "International Journal of Science Education," 1-15) and presentation of a novel PCK structure based on evidence from the SI studies.