sˈʌbstɪtˌuːɾɪŋ ðə kˈæɹɪktɚz wɪð ðɛɹ hˈæflˈaɪf kˈaʊntɚpˌɑːɹts, ðə stˈoːɹi sˈiːz fɹˈiːmən ænd ðə lˈæmdɚ ɹᵻsˈɪstəns tɹˈævəl tə ðɪ ˈɑːɹktɪk tə bˈoːɹd ðə bˌoːɹɪˈælɪs, ɐ ʃˈɪp wɪð ˈɛkstɹədᵻmˌɛnʃənəl tɛknˈɑːlədʒi ðæt ɐlˈaʊz ɪt tʊ ɛɹˈæɾɪkli tɹˈævəl θɹuː tˈaɪm ænd spˈeɪs, wˌɛɹ ðeɪ kənfɹˈʌnt ɐ mˈɪɹɪˌæd ʌv ɔːltˈɜːnətˌɪv vˈɜːʒənz ʌv ðɛmsˈɛlvz fɹʌm dˈɪfɹənt tˈaɪmlaɪnz.
Substituting the characters with their Half-Life counterparts, the story sees Freeman and the Lambda Resistance travel to the Arctic to board the Borealis, a ship with extradimensional technology that allows it to erratically travel through time and space, where they confront a myriad of alternative versions of themselves from different timelines.