Older brother of Charlie Pace, Liam grew up in England in fairly modest living conditions as the son of a butcher. When he and his brother got older, the two formed a band called Drive Shaft with Liam as lead singer. Drive Shaft played numerous local clubs before signing a record contract. In order to get Charlie on board, however, Liam promised they'll walk away if things got too crazy.
Drive Shaft's hit song "You All Everybody" catapulted the band into stardom. The fame and all the international touring led Liam to a life of sleeping with groupies, drinking, and heroin use. Liam's lifestyle took a toll on him, beginning with him missing sound checks and rehearsals, and becoming fixated with the need to get high. In one drug-induced argument with his younger brother, Liam refused to walk away like he promised and claimed that nobody cared about Charlie when it came to Drive Shaft. Liam's rampant drug use and abusive attitude eventually led to Charlie getting hooked on drugs.
Liam's drug use also led to him missing the birth of his daughter, Megan, by his girlfriend Karen. While with his daughter, Liam dropped her and was kicked out by Karen who believed he was dangerous. Karen threatened to leave Liam and take Megan with her unless he changed. In order to take care of his family, Liam sold Charlie's childhood piano without Charlie’s knowledge or consent. Liam used the money to get him, Karen and Megan to Australia. In Sydney, Karen's uncle offered to get Liam a job and Liam was able to clean up through the programs offered by a rehab clinic. Liam left behind his brother and Drive Shaft.
Living in Sydney with his family, Liam was able to stay clean and provide for them. Charlie paid Liam a visit and asked him to come back, that no one will book Drive Shaft without Liam Pace. Telling Charlie that he doesn't want to come back, Liam asked Charlie to stay with him and Karen, and they could help him kick his drug habit. But Charlie refused and left Liam behind for his flight on Oceanic 815.
- 1x07 - The Moth
- 2x12 - Fire + Water (also as a child, played by Zack Shada)
- 3x21 - Greatest Hits (also as a child, played by Zack Shada)
- 6x08 - Recon
- 6x17 - The End (1)
- 1x07 - The Moth: Coaxes Charlie into signing a record contract, leading to a downward spiral of drugs and booze. Liam cleaned up his life and is living in Sydney with his family, and tried to help Charlie clean up but his offer was rebuffed.
- 2x12 - Fire + Water: Missed his daughter's birth because he was too busy getting high. Sold Charlie's childhood piano for money so he and his family could move to Sydney.
- 1x07 - The Moth - "I AM DRIVE SHAFT! No one even knows who the sodding bass player is! This is it, Charlie. End of the rainbow. You really think you can walk away? Then what, eh? Face it. If you're not in this band, what the bloody hell use are you?