Lily and Remus were walking together, quite a distance away from James and Sirius. They were walking out near the lake, and Lily saw Severus walking near them.
“Oh no Remus, there’s Severus,” she said pointing to him.
Remus looked over to James and Sirius who were getting close to spotting Severus. He pulled out his wand and pointed it at both boys saying “Diffindo.” Their backpacks broke open and the contents spilled to the ground.
Lily let out a sigh of relief, thinking it would be a great diversion for Severus to get by – but no. He walked past them and snickered at them. Lily cried out as James managed to hang him upside down. Lily ran over, yelling at James to let him down.
James, still scared of Lily from earlier, let him drop to the ground – onto her head. She looked at Remus to do what they had discussed; “Confundus,” he said, pointing it at Severus. The confusion of Severus as Lily helped him up, most likely stopped him from retaliating and being upside-down again. Lily walked him back down towards the Slytherin common room, telling the rather confused Severus that he tripped over, bumping his head.