1917年，在格兰瑟姆老爷的催促下，玛丽给前线的马修写了一封信，告诉马修她已经与理查德先生订婚，马修十分沮丧和焦虑。虽然马修已经订婚了，这个消息却深深震撼了他。随后他告诉威廉（原唐顿庄园的男仆现为马修的勤务兵）他想跟威廉单独出门巡逻，威廉对马修突然的决定充满疑问。巡逻途中他们被德国步兵团遭到包围，导致英方报告记录他们在行动中失踪。罗伯特得知后非常震惊，但他只告诉了伊迪丝，他还跟贝茨说他爱马修把他当儿子一样。伊迪丝感到自己必须告诉玛丽马修失踪哦的消息，并非出于恶意，而是因为她知道玛丽还爱他，她得让玛丽有心理准备。不巧的是，她告诉玛丽的时候恰逢她们要为唐顿庄园疗伤的伤员们准备二重奏（伊迪丝钢琴，玛丽唱歌）。就在玛丽正唱着《如果你是世上唯一的女孩》（If you were the only girl in the world）这首歌时，马修和威廉双双出现在唐顿庄园，马修加入了歌唱，完成了这首歌。马修询问玛丽关于她订婚的事，但他说他急着赶去伦敦见拉维尼娅让玛丽有点难过。
"Maybe I'll shine by comparison." - to Lady Mary at the Downton flower show
"If you really like an argument...we should see more of each other." - to Lady Mary while sitting next to her on a bench in the garden
"Don't play with me. I don't deserve it." - to Lady Mary.
"Do you love me enough to spend the rest of your life with me? If you don't， say no. But if you do. say yes." - to Lady Mary
"I cant be sure， of you or of anything it seems"- to Lady Mary as he breaks his engagement with her.
"You've shown me I've been living in a dream and its time to return to real life. Wish me luck with that Mary， God knows I wish the best for you"- to Mary as he withdraws his proposal.
"I hardly know him， but I'm sure I'll like him when I do. That's if he's good to you. If he's not， then he has me to answer to." - talking to Mary about Sir Richard Carlisle
"You have been taking those logic pills again. We're in the army， Mason， we're going on a patrol because we're going on patrol." - talking to William in the trenches
"I keep thinking about William， and how he should be here. Not exactly instead of me， but sacrifice should be rewarded."- to Mary as she wheels him around the estate.
"You know cousin Violet came to me. Told me to marry you." - telling Mary about her grandmother's views on their relationship
"Well I couldn't could I? However much I might want to." - refering to Violets wish to break off the engagement with Lavinia and confesion that he still loves Mary
"You don't have to marry him， you know. You don't have to marry anyone. You'll always have a home here as long as I'm alive." - to Mary after he overheard an argument between her and Sir Richard
"Wanted to find out what you meant when you said you had to marry Carlisle and that I would despise you if I knew the reason" "Please tell me"- to Mary on why she still wanted to marry Carlisle even though she dislikes him.
"I never would， I never could despise you."-to Mary
"Even so， you must not marry him"- to Mary when he talks to her about calling off her engagement with Sir Richard.
"Would you stay， if I asked you too?"- asking Mary to stay instead of going to America
"You've lived your live and I've lived mine. Now it's time we live them together." - indirect proposal to Mary
"Lady Mary Crawley， Would you do me the honor in becoming my wife?"- to Mary as he proposes for the second time.
"I'm looking forward to all sort of things." - talking to Mary about life after their wedding
"It's because of something Tom said. That I won't be happy with anyone else as long as you walk the earth. Which is true! And...I think you feel the same about me." "Can I kiss you? Because I need to...very much!" - talking to Mary at her bedroom's door the night before their wedding
"You came. To be honest I wasn't completely sure you would." - to Mary at the altar.
"So there's a country boy inside the revolutionary." - to Tom Branson upon learning Tom's grandfather was a sheep farmer.