After being hit during a bombardment, Henry loses a kneecap. When he is transferred to Milan where he will have an operation, Catherine Barkley arrives at the hospital.  Henry holds her tightly when she comes to him:

"You mustn't," she said.  "You're not well enought."
"Yes, I am.  Come on."
..."Fell our hearts beating."
"I don't care about our hearts.  I want you.  I'm just mad about you."
"You really love me?"

Catherine is hesitant about lovemaking as she has already lost a fiance; however, she gives in to Henry.  Their act is for Henry, at least in part, an escape from the horrors of war. That Henry escapes his tormenting thoughts with Catherine is evinced as Catherine works night duty and sees Henry whenever she can.  Henry, then, talks with Ferguson, who suggests that Catherine take off from night duty and get some rest. Henry agrees. When Miss Gage, who declares herself Henry's "friend," enters and talks with Henry, she says that she will be glad to help him. The next day Henry learns that Catherine has taken three nights off her night duty.  When she returns, Henry states, "It was as though we met again after each of us had been away on a long journey."