▁the ▁har bour , ▁although ▁later ▁analysis ▁showed ▁that ▁the ▁reading ▁indicated ▁an ▁out bound ▁vessel ▁and ▁was ▁therefore ▁most ▁likely ▁represented ▁M - 2 4 s ▁exit . ▁M - 2 4 ▁did ▁not ▁return ▁to ▁its ▁mother ▁sub marine , ▁and ▁its ▁fate ▁remained ▁unknown ▁until ▁ 2 0 0 6 . ▁ ▁Sh ips ▁were ▁ordered ▁to ▁make ▁for ▁the ▁open ▁ocean . ▁Chicago ▁left ▁her ▁anch orage ▁at ▁ 0 2 : 1 4 , ▁leaving ▁a ▁sail or ▁behind ▁on ▁the ▁mo oring ▁bu oy ▁in ▁her ▁has te ▁to ▁depart . ▁Bomb ay , ▁Why alla , ▁Can ber ra , ▁and ▁Per kins ▁began ▁their ▁prepar ations ▁to ▁depart . ▁ ▁Just ▁before ▁ 0 3 : 0 0 , ▁as ▁Chicago ▁was ▁leaving ▁the ▁har bour , ▁the ▁look outs ▁sp otted ▁a ▁sub marine ▁per is cope ▁passing ▁alongside ▁the ▁cru iser . ▁At ▁ 0 3 : 0 1 , ▁the ▁indicator ▁loop ▁registered ▁an ▁in bound ▁signal ; ▁M - 2 1 ▁was ▁re - ent ering ▁Sydney ▁Har bour ▁after ▁recover ing ▁from ▁the ▁attack ▁four ▁hours ▁previously . ▁ ▁fired ▁on ▁M - 2 1 ▁in ▁Ne ut ral ▁Bay ▁at ▁ 0 3 : 5 0 , ▁and ▁at ▁ 0 5 : 0 0 , ▁three ▁auxili ary ▁pat rol ▁boats — H MA S ▁Ste ady ▁H our , ▁Sea ▁M ist , ▁and ▁Y ar rom a — sp otted ▁the ▁sub marine ' s ▁con