Pilot

Ian is first seen in a flashback with Melissa in the Hastings' home. Alison tells Melissa that Spencer has something to say which Spencer quickly denies. He and Melissa leave after that.

Please, Do Talk About Me When I'm Gone

At the end of the episode Ian shows up during Alison's Memorial Dedication. Spencer is just about to begin her speech when she sees him.

Keep Your Friends Close

The Liars are standing next to Hanna's locker when they spot Ian in the hallway of their school. Emily tells them he got hired as the new field hockey coach. They mention the break-up with Melissa and Spencer clarifies it was Ian who had dumped Melissa. Not the other way around. Later, Spencer hears from her sister Ian's trying to take her out for coffee, but Melissa doesn't want to. He broke her heart and she is still getting over Wren. Spencer tries to apologize for what happened, but Melissa leaves upset causing Spencer to flash back to her first encounter with Ian:

Ian and Spencer are in the garden of the Hastings' where Ian is giving her some advice on her field hockey skills. He is standing behind her showing her how to hold the stick. When he touches her arms tension arises and he proceeds to give her a gentle kiss on the back of her neck. A little surprised, Spencer turns her head and Ian kisses her passionately. ”Did you like that?”, he asks her afterwards. He then leaves Spencer alone in the garden, only for her to discover Alison was watching the whole thing, and who immediately begins to attack her for it.

Later, at the Hastings house, we see Melissa sitting in her kitchen when Ian knocks on the backdoor. Melissa is not pleased, but he begs her to have coffee with him. The liars walk in on this conversation and Spencer, out of guilt, convinces her to go and make things better. The two of them leave and Spencer confesses her secret about Ian to the girls. They even even dated for a while after he broke up with Melissa. That evening, Melissa comes to tell Spencer she actually had a really good time with Ian, indirectly thanking her. From this point on, Ian and Melissa are dating again.

At Mona's birthday party the girls are lead by ’A’ to the Alison+Ian-carving on a tree at Wright's Playground. They realize Ian was the older guy Ali was seeing. And in the last scene of the episode 'A' is watching the video of Ali the night she was killed, but now it's showing us the person she's talking to: Ian Thomas.

Moments Later

Spencer comes home late after Hanna got into the car accident at Mona's party. Melissa is comforting her when Ian shows up at the doorstep, his shirt unbuttoned suggesting he's staying with Melissa. He asks whether Hanna is alright and then informs Spencer he's cancelling Monday's practice.

During this episode the girls discover that the tree with the Alison+Ian-carving is gone. At the Hastings' house, when Aria and Spencer are discussing what could've happened to it, Ian barges in. He came to pick up two bottles of champagne. He's in a very celebratory mood and when Spencer questions him about it, Melissa joins them wearing a wedding dress and announces they got married that day. Aria and Spencer are both in shock.

The last scene shows A burning the tree with the carving of Ali and Ian.

Know Your Frenemies

Ian and Melissa are back from their honeymoon and Ian is moving in with the Hastings. It becomes obvious to Spencer they are keeping secrets when she hears them having a hushed conversation late at night. Spencer encounters Ian the next morning in her kitchen. He's making breakfast and tries to make small talk, but she's beginning to feel very wary of him. Spencer spots the tag of Hilton Head on one of his suitcases and asks questions, mentioning Alison had been there as well. This makes Ian uncomfortable and their talk dies on an uncomfortable note. Because of this Spencer channels her inner-detective during her break at school and finds out Ian was at Hilton Head the same time as Alison.

Shortly thereafter, Melissa tells her she's trying to get pregnant. Spencer is shocked they are moving things so quickly. Ian hears this and is not very happy Spencer knows.

Later that evening after a long, fruitless search through Ian's boxes the liars receive a gift from ’A’. It's the video of Alison and Ian the night she was killed and A made it look like Ian choked her to death.

Careful What U Wish 4

The girls are talking about Ian and Alison when he comes into the kitchen. The girls panic, because the laptop on the counter shows a frame of the video with Ian's face full frontal. If he noticed it at all, he did not show it. Ian acts very casual towards them and even suggests jokingly Emily should ditch the swimming team for his field hockey team.

The next day at school Hanna notices Spencer's laptop is turned on when it should be turned off and safely tucked inside her bag. Spencer checks and finds a yearbook instead. All of them are convinced Ian was the one who took it.

After school Spencer talks to Ian to ask whether he might know where her laptop is. He says he doesn't, but Spencer isn't convinced. On top of that, she learns he will be chaperoning the dance at school, which surprises her even more. He tries to explain he just really feels more comfortable back in Rosewood instead of going to Philadelphia with Melissa. ”Or at least I used to be”. She wonders what's changed and he gives her some strange explanation about how people in small towns gossip. ”They think they know you, but they don't”. This only confuses Spencer more.

At the dance Emily has gotten herself completely wasted, because of issues with Maya. In her drunk state the anger towards Ian comes up to a boiling point and just when the liars try to get her away from the situation she bolts. Emily walks up to Ian and warns him they all know what he did and that he won't get away with it. Ian pulls Spencer apart and calmly asks her to explain. She evades the truth by telling him it's because she told her friends they kissed that summer. Ian gets frustrated with her and threatens that if she's lying, ”someone is going to get hurt”.

Je Suis une Amie

Spencer stops by Ian's office at school. She lets him know she won't be at practice that day. She tries to play it off casual, but Ian takes it personally and thinks she's avoiding him. Before it can turn into a serious argument Melissa walks in looking for Ian. When she seems to be siding with Ian, Spencer decides to come clean about her plans on tutoring Toby. Melissa and Ian are both in shock and don't understand. He is suspected of murder after all, but Spencer doesn't care and leaves them to figure it out themselves.

Ian is seen in the school's courtyard as Spencer and Melissa are talking. Melissa wants Spencer to stop being so hostile to her new husband. But Spencer tells her she's worried about her and implies Ian has something to do with Alison's murder, which angers Melissa quite heavily.

Later in the evening at home, Melissa relies the news on Spencer that she's pregnant with Ian's child.

The Badass Seed

Ian and Spencer share a conversation at her home. He is sorting through his boxes and everything seems alright until he asks her for help with sealing a box. Spencer flinches and it annoys Ian. He tells her he knows about what she told Melissa about him the other day and it's not cool. He clarifies he has nothing to do with Ali's murder, but because that statement is followed by hateful comments concerning Alison, Spencer's suspicions aren't subdued. He actually refers to Ali as a ”psycho-stalker” and implies she had it coming.

Later at school, Emily and Spencer witness Ian giving something to Jenna in a paper bag.

Ian comes in during drama practice mistaking it for the Varsity Booster club. This creeps the girls out and they flash back to a time they were all still mesmerized by Ian and the older clan.

Ali had sneaked the girls into a frat party with fake IDs. Ian was in attendance too, tipsy and flirting with a girl who wasn't Melissa. Later at the party, that same girl falls down the staircase and the liars see her unconscious body lying on the floor. When Emily looked up, she saw Ian standing at the top watching the scene. He has a calm demeanor and doesn't exactly look surprised or shocked by the accident. As the girl is being driven away in an ambulance Ian is seen giving his statement to a cop. After that he observes from the porch as Alison and the girls get into the police car to go home.

In the episode they find the trophy from Hilton Head, which they think belongs to Ian. There's a giant stain on the pedestal and they assume it's Alison's blood and this is what she was murdered with. They quickly decide to hand it over to the cops.

The next day at school the liars are approached by officer Barry. He is not amused and asks them whether they planned this. The girls aren't comprehending. Gloating, he explains to them the trophy is a fake and the blood on the pedestal comes from a rat. The girls will have to come with him for questioning, again. As they walk up to the police car, Ian is watching with an insidious smile.

A Person of Interest

At the Hastings' residence, Peter and Veronica comfort Spencer, who is clearly shaken up. They suggest a therapist for her, letting her know that they have serious reservations about her version of things. Ian deftly turns the tables on Spencer, taking the spotlight off himself and placing it on her recent, erratic behavior – which has become a growing concern for her family. Melissa and Ian portray Spencer's accusation as another way for Spencer to have everything her sister has or take it away driven by jealousy.



Someone to Watch Over Me

Spencer goes on a run and when she returns, she finds Ian sitting in the dark in her living room. Speaking of running, he wants to help Spencer run away and tells her she should take the help now while he's offering it. He emphasizes the urgency of the situation because when she's arrested, it'll be too late.

Monsters in the End

At the festival, Spencer and Ian continue to play a mental chess game with each other. They set up cupcakes for the booth, while chatty Mrs. Ackard brings up Hilton Resorts in South Carolina, and Spencer uses the opportunity to catch Ian in a lie.

Later at the festival, Ian corners Spencer and lets her know that she better be careful, because she is sinking fast. Spencer just purses her lips at him.

Later Spencer comes face to face with Ian again who is holding the crowbar. She expects him to strike her, but he is with the rest of the family, who are worried about her.They criticize the negligence of the management.

For Whom the Bell Tolls

Ian is nowhere to be found after Melissa and Spencer get into a car accident, leaving Melissa's unborn child to be carefully monitored in the hospital. When Spencer is looking for Melissa's cell phone in the church, Ian attempts to kill her, learning that Spencer was the one leaving anonymous ultimatums on his phone. While there, he seems to admit to killing Alison and tells Spencer he's going to have to do the same to her.

In an attempt to escape, Spencer throws away the only piece of evidence linked to Ian: the flashdrive, with Ian's "footage." She runs throughout the church until finally Ian catches up with her, attempting to throw her over the bell tower landing. Spencer begs for Ian to let her go, with the rest of the Liars on the phone overhearing the exchange. Suddenly, Ian sees a dark hooded figure coming his way. Ian asks the figure "What are you doing here?". The figure responded by throwing Ian over the landing where a rope ties around his throat hanging him off the landing. When, Hanna, Aria and Emily get to the church, they find a traumatized Spencer alone, with Ian hanging off the landing, seemingly dead. When the police arrive at the church, Ian is mysteriously missing.