/usr/lib/emboss/include/eplplot/ is in emboss-lib 6.6.0+dfsg-3build1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/emboss/include/eplplot/disptab.h
/usr/lib/emboss/include/eplplot/drivers.h
/usr/lib/emboss/include/eplplot/metadefs.h
/usr/lib/emboss/include/eplplot/pdf.h
/usr/lib/emboss/include/eplplot/plConfig.h
/usr/lib/emboss/include/eplplot/plDevs.h
/usr/lib/emboss/include/eplplot/plcore.h
/usr/lib/emboss/include/eplplot/pldebug.h
/usr/lib/emboss/include/eplplot/pldll.h
/usr/lib/emboss/include/eplplot/plevent.h
/usr/lib/emboss/include/eplplot/plfci-type1.h
/usr/lib/emboss/include/eplplot/plhershey-unicode.h
/usr/lib/emboss/include/eplplot/plplot.h
/usr/lib/emboss/include/eplplot/plplotP.h
/usr/lib/emboss/include/eplplot/plstrm.h
/usr/lib/emboss/include/eplplot/plunicode-type1.h
/usr/lib/emboss/include/eplplot/plxwd.h
/usr/lib/emboss/include/eplplot/ps.h