you added the murder of Pleuratus to that of Plator

    accessiō ōnis, f    [accedo], a coming to, approach; hence, is suo labore suisque accessionibus consequebatur, ut, etc., by his personal appeals, visits. — Praegn.; abstr., an increase, enlargement, addition: accessiones fortunae et dignitatis: paucorum annorum; concr., an addition, augment, contribution, reinforcement, appendix: quadraginta militum: nummorum: alqd accessionis dare, conferre, by way of addition: decumae, an addition to a tax: tibi etiam accessio fuit ad necem Platoris Pleuratus, i. e. you added the murder of Pleuratus to that of Plator.