A really easy stitch that looks more complicated than it is. The Thorn stitch is an eight row repeat and is knitted in a multiple of four stitches plus one.

Row 1 (Right side): Color A, k2, * (k1, yo, k1) in next stitch, k3; repeat from * to last 3 sts, (k1, yo, k1) in next stitch, k2.
Row 2: Color B, p2, * sl 3 wyif, p3; repeat from * to last 3 sts, sl 3 wyif, p2
Row 3: Color B, k1, * k2 tog, sl 1 wyib, ssk, k1; repeat from * to end.
Row 4: Color A, p4. * sl 1 wyif, p3; repeat from * to last st, p1.
Row 5: Color A, k4, * (k1, yo, k1) in next stitch, k3; repeat from * to last st, k1.
Row 6: Color B, p4, * sl 3 wyif, p3; repeat from * to last st, p1.
Row 7: Color B, k3, * k2 tog, sl 1 wyib, ssk, k1; repeat from * to last 2 sts, k2.
Row 8: Color A, p2, * sl 1 wyif, p3; repeat from * to last 3 sts, sl 1 wyif, p2.

Knitting abbreviations:
Knit: K | Purl: P | Yarn over: Yo | Knit 2 sts together: K2tog | Slip slip knit: Ssk.
Slip stitch purlwise with yarn in front: Sl wyif
Watch this video to learn how to knit the two-color thorn stitch.