Heretics within charts the theological controversies surrounding two London Puritan pastors, Anthony Wotton (c.1561–1626) and John Goodwin (c. 1594–1665). The doctrine of justification links these two divines, who both opposed the imputationist consensus of the Reformed tradition. Parnham dubs Goodwin a ‘disciple’ of Wotton, continuing his master's fight against legalism (an inherent danger of the imputation of forensic righteousness), and antinomianism (an immanent threat among the godly). By fighting on these fronts, Wotton and Goodwin take turns as public enemy number one for the heresy hunter George Walker. Parnham's vivid prose captures the aggression that accompanied these debates as Walker fought off Wotton the ‘wolf’ and then Goodwin the ‘red dragon’. An introductory chapter attempts a brief placement of the book amidst the burgeoning secondary literature on Puritan theology in general and these two divines in particular. Part i then charts the discourse and debates of Wotton who sought to use reformed authorities (the Fathers and the Reformers), to modify the commitment of Reformed Orthodoxy to imputationism. Part ii traces the contours of Goodwin's early writings, especially the Treatise of justification and argues for significant continuity with Wotton. Parnham then continues beyond justification to a wider-ranging discussion of Goodwin's soteriological writings, including a long chapter on his magnum opus: Redemption redeemed. These chapters give extensive description of both the theological texts and their controversial reception by other divines. The style of Heretics within is like that of a cartographer moving through primary sources to trace the contours of theological argumentation. Parnham accurately maps these complex texts, which include intricate scholastic logic and extensive use of the trium linguarum in the marginalia. As such, Heretics within makes an original contribution by exceeding the level of detail achieved to date, including that of Coffey's intellectual biography of Goodwin. However, readers of Heretics within may also be left with some questions: was Goodwin really Wotton's ‘disciple’? This is emphasised in the early chapters to give the two characters in the book a unitive cohesion. However, Parnham struggles sufficiently to evidence the level of influence that he attributes, especially given that any debt to Wotton was ‘unacknowledged’ (p.183). Then, for the final five chapters of the book, Wotton's voice falls silent altogether as Goodwin's Arminian soteriology is discussed. Greater cohesion might have been achieved by considering the soteriological differences of the central characters as well as their solifidian similarities. Heretics within also leaves the reader with the question: ‘So what?’ Parnham's thick description of theological texts struggles to reach weighty conclusions. With a title that raises the issue of boundaries and identities (Heretics within), one expects some engagement with the nature of English Puritanism and the scope of Reformed and Arminian categories. However Parnham's cartography seems restricted to local and individual description with little reference to the wider context. As a result, there is minimal engagement with current scholarship on Puritanism and Reformed Orthodoxy, despite Coffey's monograph demonstrating the pertinence of Goodwin on numerous fronts. Though Parnham gives voice to a plethora of individual interlocutors (Perkins, Pemble, Twisse, Baxter, Owen and others) the book remains at the level of at times repetitive description. Heretics within is a thorough and accurate guide for those wanting a local read around two controversial Puritan voices on justification. However, those hoping for a wider perspective on seventeenth-century theological debates and confessional boundaries may be disappointed.