en_tn/act/25/03.md

asked him for a favor

Here the word "him" refers to Festus.

that Festus might summon Paul to Jerusalem

This means that Festus would order his soldiers to bring Paul to Jerusalem. Alternate translation: "that he might order his soldiers to bring Paul to Jerusalem"

so that they could kill him along the way

They were going to ambush Paul, but Festus was not aware of this part of their plan.