diff --git a/backend/internal/http/handlers.go b/backend/internal/http/handlers.go
index 9236095..54b1079 100644
--- a/backend/internal/http/handlers.go
+++ b/backend/internal/http/handlers.go
@@ -30,5 +30,33 @@ func NewRouter(svc service.EpisodeService) *gin.Engine {
 		c.JSON(http.StatusOK, cur)
 	})
 
+	type setCurrentReq struct {
+		ID        int64  `json:"id" binding:"required"`
+		StartTime string `json:"start_time" binding:"required"` // HH:MM or HH:MM:SS
+	}
+
+	r.POST("/current", func(c *gin.Context) {
+		var req setCurrentReq
+		if err := c.ShouldBindJSON(&req); err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid payload"})
+			return
+		}
+		cur, err := svc.SetCurrent(c.Request.Context(), req.ID, req.StartTime)
+		if err != nil {
+			switch err {
+			case service.ErrInvalidTime:
+				c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+				return
+			case repo.ErrNotFound:
+				c.JSON(http.StatusNotFound, gin.H{"error": "id not found"})
+				return
+			default:
+				c.JSON(http.StatusInternalServerError, gin.H{"error": "update failed"})
+				return
+			}
+		}
+		c.JSON(http.StatusOK, cur)
+	})
+
 	return r
 }
diff --git a/backend/internal/repo/episode_repo.go b/backend/internal/repo/episode_repo.go
index ffd6813..5973b1f 100644
--- a/backend/internal/repo/episode_repo.go
+++ b/backend/internal/repo/episode_repo.go
@@ -22,6 +22,7 @@ type Episode struct {
 
 type EpisodeRepository interface {
 	GetCurrent(ctx context.Context) (Episode, error)
+	SetCurrent(ctx context.Context, id int64, startHHMMSS string) error
 }
 
 type pgxEpisodeRepo struct {
@@ -58,3 +59,27 @@ LIMIT 1;
 	}
 	return e, nil
 }
+
+func (r *pgxEpisodeRepo) SetCurrent(ctx context.Context, id int64, startHHMMSS string) error {
+	tx, err := r.pool.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = tx.Rollback(ctx) }()
+
+	// 1) clear any current episode flag
+	if _, err := tx.Exec(ctx, `UPDATE current SET current_ep = false WHERE current_ep = true`); err != nil {
+		return err
+	}
+
+	// 2) set start_time and current_ep for the id
+	ct, err := tx.Exec(ctx, `UPDATE current SET start_time = $1::time, current_ep = true WHERE id = $2`, startHHMMSS, id)
+	if err != nil {
+		return err
+	}
+	if ct.RowsAffected() == 0 {
+		return ErrNotFound
+	}
+
+	return tx.Commit(ctx)
+}
diff --git a/backend/internal/service/episode_service.go b/backend/internal/service/episode_service.go
index 72c0c96..5758cae 100644
--- a/backend/internal/service/episode_service.go
+++ b/backend/internal/service/episode_service.go
@@ -2,13 +2,18 @@ package service
 
 import (
 	"context"
+	"errors"
+	"strings"
 	"time"
 
 	"watch-party-backend/internal/repo"
 )
 
+var ErrInvalidTime = errors.New("invalid start_time (expected HH:MM or HH:MM:SS)")
+
 type EpisodeService interface {
 	GetCurrent(ctx context.Context) (repo.Episode, error)
+	SetCurrent(ctx context.Context, id int64, start string) (repo.Episode, error)
 }
 
 type episodeService struct {
@@ -20,8 +25,38 @@ func NewEpisodeService(r repo.EpisodeRepository) EpisodeService {
 }
 
 func (s *episodeService) GetCurrent(ctx context.Context) (repo.Episode, error) {
-	// Add cross-cutting concerns here (timeouts, metrics, caching, etc.)
 	c, cancel := context.WithTimeout(ctx, 3*time.Second)
 	defer cancel()
 	return s.repo.GetCurrent(c)
 }
+
+func (s *episodeService) SetCurrent(ctx context.Context, id int64, start string) (repo.Episode, error) {
+	// normalize and validate time as HH:MM:SS
+	normalized, err := normalizeHHMMSS(start)
+	if err != nil {
+		return repo.Episode{}, ErrInvalidTime
+	}
+
+	c, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
+
+	// do the transaction
+	if err := s.repo.SetCurrent(c, id, normalized); err != nil {
+		return repo.Episode{}, err
+	}
+	// return the new current row
+	return s.repo.GetCurrent(c)
+}
+
+func normalizeHHMMSS(s string) (string, error) {
+	s = strings.TrimSpace(s)
+	if len(s) == 5 { // HH:MM → append seconds
+		s += ":00"
+	}
+	// Strict parse/format to 24h
+	t, err := time.Parse("15:04:05", s)
+	if err != nil {
+		return "", err
+	}
+	return t.Format("15:04:05"), nil
+}