This paper is a continuation of the article published in the previous issue of 'Prospettiva' by Vittoria Pipino and the present writer, extending the research on the 14-century church to the construction and decoration of the Spinelli chapel. Of particular importance within the iconographic programme – aimed at celebrating the dies natalis of Saints John the Baptist and John the Evangelist – is the sanctorale devoted to the blessed Servites, which provides chronological references for the frescoes and reveals the intrusiveness of the congregation in the decoration of a chapel of private patronage. The research also aims to clarify the authorship of the paintings, long debated by 20th-century scholars, who considered the Spinelli and Petroni frescoes to be the product of the same decorative campaign. Alongside the presence of Niccolò di Segna, already identified in recent critical literature, the hand of Bartolomeo Bulgarini is proposed. The final pages are dedicated to the fragmentary 'Last Judgement' on the counterfaçade and the 'Madonna delle anime'. The cult of the Virgin as advocata peccatorum, represented here also as the Madonna of the mantle, must have been very popular with the Servites, as the frescoes of the congregations of Pavia and Todi demonstrate.